Siga este link para ver outros tipos de publicações sobre o tema: Enzymes.
Artigos de revistas sobre o tema "Enzymes"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Veja os 50 melhores artigos de revistas para estudos sobre o assunto "Enzymes".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Veja os artigos de revistas das mais diversas áreas científicas e compile uma bibliografia correta.
1
Stitt, M. "The Use of Transgenic Plants to Study the Regulation of Plant Carbohydrate Metabolism". Functional Plant Biology 22, n.º 4 (1995): 635. http://dx.doi.org/10.1071/pp9950635.
Texto completo da fonteResumo:
Transgenic plants with decreased expression of specific enzymes provide a powerful new tool to investigate metabolic regulation. Their use is discussed in the context of theories of metabolic regulation. It is argued that an enzyme is a key site for regulation, in the strict sense, when (i) natural mechanisms exist to alter the activity of the enzyme in vivo ('regulatability'), and (ii) a change in the activity of the enzyme is able to lead to a change in flux through the pathway ('regulatory capacity'). Previous approaches to the study of regulation allow the identification of enzymes with high 'regulatability', but they do not provide consistent or valid criteria to assess their 'regulatory capacity'. They therefore do not distinguish between enzymes which actually control metabolic fluxes, and enzymes which just respond to changes initiated elsewhere in the pathway. They may also underestimate the contribution of enzymes that catalyse reversible reactions. In contrast, mutants and transgenic plants can be used to directly test the importance of different aspects of an enzyme's regulatory properties in vivo. Even more importantly, they provide a method to determine flux control coefficients which provide a quantitative measure of an enzyme's 'regulatory capacity'. Recent results are surnrnarised, and potential practical problems in measuring control coefficients are reviewed.
2
Christensen, Stefan Jarl, Silke Flindt Badino, Ana Mafalda Cavaleiro, Kim Borch e Peter Westh. "Functional analysis of chimeric TrCel6A enzymes with different carbohydrate binding modules". Protein Engineering, Design and Selection 32, n.º 9 (setembro de 2019): 401–9. http://dx.doi.org/10.1093/protein/gzaa003.
Texto completo da fonteResumo:
Abstract The glycoside hydrolase (GH) family 6 is an important group of enzymes that constitute an essential part of industrial enzyme cocktails used to convert lignocellulose into fermentable sugars. In nature, enzymes from this family often have a carbohydrate binding module (CBM) from the CBM family 1. These modules are known to promote adsorption to the cellulose surface and influence enzymatic activity. Here, we have investigated the functional diversity of CBMs found within the GH6 family. This was done by constructing five chimeric enzymes based on the model enzyme, TrCel6A, from the soft-rot fungus Trichoderma reesei. The natural CBM of this enzyme was exchanged with CBMs from other GH6 enzymes originating from different cellulose degrading fungi. The chimeric enzymes were expressed in the same host and investigated in adsorption and quasi-steady-state kinetic experiments. Our results quantified functional differences of these phylogenetically distant binding modules. Thus, the partitioning coefficient for substrate binding varied 4-fold, while the maximal turnover (kcat) showed a 2-fold difference. The wild-type enzyme showed the highest cellulose affinity on all tested substrates and the highest catalytic turnover. The CBM from Serendipita indica strongly promoted the enzyme’s ability to form productive complexes with sites on the substrate surface but showed lower turnover of the complex. We conclude that the CBM plays an important role for the functional differences between GH6 wild-type enzymes.
3
Nixon, Andrew E., Marc Ostermeier e Stephen J. Benkovic. "Hybrid enzymes: manipulating enzyme design". Trends in Biotechnology 16, n.º 6 (junho de 1998): 258–64. http://dx.doi.org/10.1016/s0167-7799(98)01204-9.
Texto completo da fonte
4
Memon, Safyan Aman, Kinaan Aamir Khan e Hammad Naveed. "HECNet: a hierarchical approach to enzyme function classification using a Siamese Triplet Network". Bioinformatics 36, n.º 17 (25 de maio de 2020): 4583–89. http://dx.doi.org/10.1093/bioinformatics/btaa536.
Texto completo da fonteResumo:
Abstract Motivation Understanding an enzyme’s function is one of the most crucial problem domains in computational biology. Enzymes are a key component in all organisms and many industrial processes as they help in fighting diseases and speed up essential chemical reactions. They have wide applications and therefore, the discovery of new enzymatic proteins can accelerate biological research and commercial productivity. Biological experiments, to determine an enzyme’s function, are time-consuming and resource expensive. Results In this study, we propose a novel computational approach to predict an enzyme’s function up to the fourth level of the Enzyme Commission (EC) Number. Many studies have attempted to predict an enzyme’s function. Yet, no approach has properly tackled the fourth and final level of the EC number. The fourth level holds great significance as it gives us the most specific information of how an enzyme performs its function. Our method uses innovative deep learning approaches along with an efficient hierarchical classification scheme to predict an enzyme’s precise function. On a dataset of 11 353 enzymes and 402 classes, we achieved a hierarchical accuracy and Macro-F1 score of 91.2% and 81.9%, respectively, on the 4th level. Moreover, our method can be used to predict the function of enzyme isoforms with considerable success. This methodology is broadly applicable for genome-wide prediction that can subsequently lead to automated annotation of enzyme databases and the identification of better/cheaper enzymes for commercial activities. Availability and implementation The web-server can be freely accessed at http://hecnet.cbrlab.org/. Supplementary information Supplementary data are available at Bioinformatics online.
5
Cieśla, Joanna. "Metabolic enzymes that bind RNA: yet another level of cellular regulatory network?" Acta Biochimica Polonica 53, n.º 1 (12 de janeiro de 2006): 11–32. http://dx.doi.org/10.18388/abp.2006_3360.
Texto completo da fonteResumo:
Several enzymes that were originally characterized to have one defined function in intermediatory metabolism are now shown to participate in a number of other cellular processes. Multifunctional proteins may be crucial for building of the highly complex networks that maintain the function and structure in the eukaryotic cell possessing a relatively low number of protein-encoding genes. One facet of this phenomenon, on which I will focus in this review, is the interaction of metabolic enzymes with RNA. The list of such enzymes known to be associated with RNA is constantly expanding, but the most intriguing question remains unanswered: are the metabolic enzyme-RNA interactions relevant in the regulation of cell metabolism? It has been proposed that metabolic RNA-binding enzymes participate in general regulatory circuits linking a metabolic function to a regulatory mechanism, similar to the situation of the metabolic enzyme aconitase, which also functions as iron-responsive RNA-binding regulatory element. However, some authors have cautioned that some of such enzymes may merely represent "molecular fossils" of the transition from an RNA to a protein world and that the RNA-binding properties may not have a functional significance. Here I will describe enzymes that have been shown to interact with RNA (in several cases a newly discovered RNA-binding protein has been identified as a well-known metabolic enzyme) and particularly point out those whose ability to interact with RNA seems to have a proven physiological significance. I will also try to depict the molecular switch between an enzyme's metabolic and regulatory functions in cases where such a mechanism has been elucidated. For most of these enzymes relations between their enzymatic functions and RNA metabolism are unclear or seem not to exist. All these enzymes are ancient, as judged by their wide distribution, and participate in fundamental biochemical pathways.
6
Page, Michael I. "Past times: The efficiency of enzyme catalysis". Biochemist 25, n.º 4 (1 de agosto de 2003): 52–53. http://dx.doi.org/10.1042/bio02504052.
Texto completo da fonteResumo:
Understanding enzyme catalysis on a molecular and energetic basis has fascinated scientists for more than half a century. In addition to their obvious physiological involvement, the incredible efficiency of enzymes continues to intrigue us. In the absence of enzymes, many reactions of biological interest, e.g. the hydrolysis of proteins, carbohydrates and DNA, have half-lives of hundreds to millions of years. After a substrate is bound at an enzyme's active site, its halflife is usually milliseconds. The low concentration of enzymes in cells, which is often at or below the micromolar level, means that a rapid turnover is necessary to produce a significant rate of reaction and many reactions occur at near the diffusion controlled limit. The high catalytic efficiency of enzymes has not been emulated by artificial systems and therefore many have wondered if they could even be understood by ordinary chemistry.
7
March, John B., e Jason Clark. "Enzymes by post—restriction enzyme stability". Nature Biotechnology 18, n.º 3 (março de 2000): 243. http://dx.doi.org/10.1038/73590.
Texto completo da fonte
8
Städler, Brigitte, e Alexander N. Zelikin. "Enzyme prodrug therapies and therapeutic enzymes". Advanced Drug Delivery Reviews 118 (setembro de 2017): 1. http://dx.doi.org/10.1016/j.addr.2017.10.006.
Texto completo da fonte
9
Howell, Matthew, Daniel G. Dumitrescu, Lauren R. Blankenship, Darby Herkert e Stavroula K. Hatzios. "Functional characterization of a subtilisin-like serine protease from Vibrio cholerae". Journal of Biological Chemistry 294, n.º 25 (10 de maio de 2019): 9888–900. http://dx.doi.org/10.1074/jbc.ra119.007745.
Texto completo da fonteResumo:
Vibrio cholerae, the causative agent of the human diarrheal disease cholera, exports numerous enzymes that facilitate its adaptation to both intestinal and aquatic niches. These secreted enzymes can mediate nutrient acquisition, biofilm assembly, and V. cholerae interactions with its host. We recently identified a V. cholerae-secreted serine protease, IvaP, that is active in V. cholerae-infected rabbits and human choleric stool. IvaP alters the activity of several host and pathogen enzymes in the gut and, along with other secreted V. cholerae proteases, decreases binding of intelectin, an intestinal carbohydrate-binding protein, to V. cholerae in vivo. IvaP bears homology to subtilisin-like enzymes, a large family of serine proteases primarily comprised of secreted endopeptidases. Following secretion, IvaP is cleaved at least three times to yield a truncated enzyme with serine hydrolase activity, yet little is known about the mechanism of extracellular maturation. Here, we show that IvaP maturation requires a series of sequential N- and C-terminal cleavage events congruent with the enzyme's mosaic protein domain structure. Using a catalytically inactive reporter protein, we determined that IvaP can be partially processed in trans, but intramolecular proteolysis is most likely required to generate the mature enzyme. Unlike many other subtilisin-like enzymes, the IvaP cleavage pattern is consistent with stepwise processing of the N-terminal propeptide, which could temporarily inhibit, and be cleaved by, the purified enzyme. Furthermore, IvaP was able to cleave purified intelectin, which inhibited intelectin binding to V. cholerae. These results suggest that IvaP plays a role in modulating intelectin–V. cholerae interactions.
10
Jimoh, Abdulhameed, e Job Atteh. "Improving the metabolisable energy value of brewers’ dried grains with enzyme cocktails in poultry nutrition". Journal of Agricultural Sciences, Belgrade 63, n.º 4 (2018): 409–19. http://dx.doi.org/10.2298/jas1804409j.
Texto completo da fonteResumo:
The determination of the positive effects of exogenous enzymes is essential to ensure their inclusion in poultry feed formulation. This study was conducted to determine the effect of enzymes on the apparent metabolisable energy (AME) value of brewers? dried grain (BDG). Xylanase, phytase and multipurpose enzymes were used in a completely randomised design to determine the effects of individual exogenous enzymes and their cocktails on poultry metabolisable energy using adult cockerels. There were eight treatments comprising a control and seven experimental treatments with BDG and one, two or three enzymes. The AME values were determined using the intubation method. Data collected were analysed using the statistical analysis system. Enzymes individually and as a cocktail improved the AME value of BDG compared to the control. An increase in the AME value was 3.48%, 5.39%, 5.92%, 14.29%, 18.13%, 23.21% and 29.58% respectively for phytase, xylanase, cocktail of xylanase and phytase, multipurpose enzyme, cocktail of multipurpose enzyme and phytase, cocktail of xylanase and multipurpose enzyme and cocktail of xylanase, phytase and multipurpose enzyme. Cocktails of enzymes were significantly better (P?0.05) than individual enzymes in their effects on apparent metabolisable energy of BDG. Phytase gave a marginal increase in AME of the studied feedstuff. It has been concluded that the cocktail of enzymes is better than individual enzymes in their effects on AME of BDG. If different enzymes are available, it is recommended that the enzyme with higher units should be used.
11
Høst, Amalie Vang, Roberto Morellon-Sterling, Diego Carballares, John M. Woodley e Roberto Fernandez-Lafuente. "Co-Enzymes with Dissimilar Stabilities: A Discussion of the Likely Biocatalyst Performance Problems and Some Potential Solutions". Catalysts 12, n.º 12 (3 de dezembro de 2022): 1570. http://dx.doi.org/10.3390/catal12121570.
Texto completo da fonteResumo:
Enzymes have several excellent catalytic features, and the last few years have seen a revolution in biocatalysis, which has grown from using one enzyme to using multiple enzymes in cascade reactions, where the product of one enzyme reaction is the substrate for the subsequent one. However, enzyme stability remains an issue despite the many benefits of using enzymes in a catalytic system. When enzymes are exposed to harsh process conditions, deactivation occurs, which changes the activity of the enzyme, leading to an increase in reaction time to achieve a given conversion. Immobilization is a well-known strategy to improve many enzyme properties, if the immobilization is properly designed and controlled. Enzyme co-immobilization is a further step in the complexity of preparing a biocatalyst, whereby two or more enzymes are immobilized on the same particle or support. One crucial problem when designing and using co-immobilized enzymes is the possibility of using enzymes with very different stabilities. This paper discusses different scenarios using two co-immobilized enzymes of the same or differing stability. The effect on operational performance is shown via simple simulations using Michaelis–Menten equations to describe kinetics integrated with a deactivation term. Finally, some strategies for overcoming some of these problems are discussed.
12
Liu, Jie, e Joseph Wang. "Remarkable thermostability of bioelectrodes based on enzymes immobilized within hydrophobic semi‐solid matrices". Biotechnology and Applied Biochemistry 30, n.º 2 (outubro de 1999): 177–83. http://dx.doi.org/10.1111/j.1470-8744.1999.tb00910.x.
Texto completo da fonteResumo:
An enhanced resistance to thermal denaturation was investigated for enzymes immobilized within hydrophobic semi‐solid matrices compared with both free enzymes and polymer‐entrapped enzymes. The bioelectrodes based on the immobilization of glucose oxidase, lactate oxidase, alcohol oxidase, polyphenol oxidase, peroxidase and L‐amino acid oxidase within a carbon‐paste matrix were constructed to examine their thermal stabilitiy at 60 °C or 80 °C. The rhodium/glucose oxidase‐containing carbon‐paste electrode was found to offer a remarkable stability when incubated at 60 °C over a long period of 4 months, with only a decrease of approx. 15% in activity. The comparative studies suggest that thermal stabilization established by this enzyme‐immobilization procedure varies with the enzyme’s inherent stability, the incubation temperature and the immobilizing reagent, such as pasting liquid.
13
Mokhtar, Nur Fathiah, Raja Noor Zaliha Raja Abd. Rahman, Noor Dina Muhd Noor, Fairolniza Mohd Shariff e Mohd Shukuri Mohamad Ali. "The Immobilization of Lipases on Porous Support by Adsorption and Hydrophobic Interaction Method". Catalysts 10, n.º 7 (4 de julho de 2020): 744. http://dx.doi.org/10.3390/catal10070744.
Texto completo da fonteResumo:
Four major enzymes commonly used in the market are lipases, proteases, amylases, and cellulases. For instance, in both academic and industrial levels, microbial lipases have been well studied for industrial and biotechnological applications compared to others. Immobilization is done to minimize the cost. The improvement of enzyme properties enables the reusability of enzymes and facilitates enzymes used in a continuous process. Immobilized enzymes are enzymes physically confined in a particularly defined region with retention to their catalytic activities. Immobilized enzymes can be used repeatedly compared to free enzymes, which are unable to catalyze reactions continuously in the system. Immobilization also provides a higher pH value and thermal stability for enzymes toward synthesis. The main parameter influencing the immobilization is the support used to immobilize the enzyme. The support should have a large surface area, high rigidity, suitable shape and particle size, reusability, and resistance to microbial attachment, which will enhance the stability of the enzyme. The diffusion of the substrate in the carrier is more favorable on hydrophobic supports instead of hydrophilic supports. The methods used for enzyme immobilization also play a crucial role in immobilization performance. The combination of immobilization methods will increase the binding force between enzymes and the support, thus reducing the leakage of the enzymes from the support. The adsorption of lipase on a hydrophobic support causes the interfacial activation of lipase during immobilization. The adsorption method also causes less or no change in enzyme conformation, especially on the active site of the enzyme. Thus, this method is the most used in the immobilization process for industrial applications.
14
Ioannou, Y. A., D. F. Bishop e R. J. Desnick. "Overexpression of human alpha-galactosidase A results in its intracellular aggregation, crystallization in lysosomes, and selective secretion." Journal of Cell Biology 119, n.º 5 (1 de dezembro de 1992): 1137–50. http://dx.doi.org/10.1083/jcb.119.5.1137.
Texto completo da fonteResumo:
Human lysosomal alpha-galactosidase A (alpha-Gal A) was stably overexpressed in CHO cells and its biosynthesis and targeting were investigated. Clone AGA5.3-1000Mx, which was the highest enzyme overexpressor, produced intracellular alpha-Gal A levels of 20,900 U/mg (approximately 100 micrograms of enzyme/10(7) cells) and secreted approximately 13,000 U (or 75 micrograms/10(7) cells) per day. Ultrastructural examination of these cells revealed numerous 0.25-1.5 microns crystalline structures in dilated trans-Golgi network (TGN) and in lysosomes which stained with immunogold particles using affinity-purified anti-human alpha-Gal A antibodies. Pulse-chase studies revealed that approximately 65% of the total enzyme synthesized was secreted, while endogenous CHO lysosomal enzymes were not, indicating that the alpha-Gal A secretion was specific. The recombinant intracellular and secreted enzyme forms were normally processed and phosphorylated; the secreted enzyme had mannose-6-phosphate moieties and bound the immobilized 215-kD mannose-6-phosphate receptor (M6PR). Thus, the overexpressed enzyme's selective secretion did not result from oversaturation of the M6PR-mediated pathway or abnormal binding to the M6PR. Of note, the secreted alpha-Gal A was sulfated and the percent of enzyme sulfation decreased with increasing amplification, presumably due to the inaccessibility of the enzyme's tyrosine residues for the sulfotransferase in the TGN. Overexpression of human lysosomal alpha-N-acetylgalactosaminidase and acid sphingomyelinase in CHO cell lines also resulted in their respective selective secretion. In vitro studies revealed that purified secreted alpha-Gal A was precipitated as a function of enzyme concentration and pH, with 30% of the soluble enzyme being precipitated when 10 mg/ml of enzyme was incubated at pH 5.0. Thus, it is hypothesized that these overexpressed lysosomal enzymes are normally modified until they reach the TGN where the more acidic environment of this compartment causes the formation of soluble and particulate enzyme aggregates. A significant proportion of these enzyme aggregates are unable to bind the M6PR and are selectively secreted via the constitutive secretory pathway, while endogenous lysosomal enzymes bind the M6PRs and are transported to lysosomes.
15
Vikhrova, А. O., S. L. Yuzkiv, I. R. Buchkevych, М. S. Kurka e V. I. Lubenets. "USE OF ENZYMES AND ENZYME PREPARATIONS IN FOOD TECHNOLOGIES". Chemistry, Technology and Application of Substances 5, n.º 2 (1 de dezembro de 2022): 118–35. http://dx.doi.org/10.23939/ctas2022.02.118.
Texto completo da fonteResumo:
The analysis of literature sources on the use of enzymes, enzyme preparations and immobilized enzymes, allowed to determine which enzymes are used in certain sectors of the food industry. It is established that the condition for the use of enzymes in the food industry is the availability, low cost and inertia relative to the target product. Examples of the wide use of enzymes, enzyme preparations and immobilized enzymes in the technological processes of the food industry are given, which contribute to improving the quality of food products and improving their storage conditions.
16
Hochendoner, Philip, Curtis Ogle e William H. Mather. "A queueing approach to multi-site enzyme kinetics". Interface Focus 4, n.º 3 (6 de junho de 2014): 20130077. http://dx.doi.org/10.1098/rsfs.2013.0077.
Texto completo da fonteResumo:
Multi-site enzymes, defined as where multiple substrate molecules can bind simultaneously to the same enzyme molecule, play a key role in a number of biological networks, with the Escherichia coli protease ClpXP a well-studied example. These enzymes can form a low latency ‘waiting line’ of substrate to the enzyme's catalytic core, such that the enzyme molecule can continue to collect substrate even when the catalytic core is occupied. To understand multi-site enzyme kinetics, we study a discrete stochastic model that includes a single catalytic core fed by a fixed number of substrate binding sites. A natural queueing systems analogy is found to provide substantial insight into the dynamics of the model. From this, we derive exact results for the probability distribution of the enzyme configuration and for the distribution of substrate departure times in the case of identical but distinguishable classes of substrate molecules. Comments are also provided for the case when different classes of substrate molecules are not processed identically.
17
Siregar, Benedicta Lamria, Rexi Sebastian Siallagan, Suwarnita Butar Butar, Bambang Mahmudi e Elisabeth Sri Pujiastuti. "The Nutrient Content of Eco-enzymes from Mixture of Various Fruit Peels". Agro Bali : Agricultural Journal 7, n.º 2 (31 de julho de 2024): 475–87. http://dx.doi.org/10.37637/ab.v7i2.1646.
Texto completo da fonteResumo:
Today, many institutions and individuals are paying attention to the development of technologies used in sustainable agriculture. One of the technologies is eco-enzyme that can be used as organic fertilizer. Several researchers have studied the use of eco-enzymes in agriculture, but studies on the nutrient content of eco-enzymes are still very limited. This research was conducted to investigate the nutrient content of two eco-enzyme preparations. The eco-enzymes were produced through the fermentation process of water, fruit peels, and molasses with a weight ratio of 10 : 3 : 1. Fruit peels used for Eco-enzyme A were banana, melon, watermelon, orange, and pineapple peels, while for Eco-enzyme B were banana, mango, watermelon, orange, and pineapple peels. The fermentation period for Eco-enzyme A was seven months, while for Eco-enzyme B was eight months. The results of the analysis showed that the two eco-enzymes contained various nutrients, both macro (C, N, P, K, Mg, Ca) and micro (Mn, Zn, B, Fe, Cu) ones, that were consistently higher in Eco-enzyme A. Both eco-enzymes were acidic, where the pH of Eco-enzyme A and B were 3.95 and 3.50, respectively. The data obtained were expected to be a basic reference for further research on eco-enzymes.
18
Galperin, Michael Y., D. Roland Walker e Eugene V. Koonin. "Analogous Enzymes: Independent Inventions in Enzyme Evolution". Genome Research 8, n.º 8 (1 de agosto de 1998): 779–90. http://dx.doi.org/10.1101/gr.8.8.779.
Texto completo da fonte
19
Lieberman, Jack. "Enzymes in Sarcoidosis: Angiotensin-Converting-Enzyme (ACE)". Clinics in Laboratory Medicine 9, n.º 4 (dezembro de 1989): 745–56. http://dx.doi.org/10.1016/s0272-2712(18)30602-4.
Texto completo da fonte
20
Maeda, Masako. "New label enzymes for bioluminescent enzyme immunoassay". Journal of Pharmaceutical and Biomedical Analysis 30, n.º 6 (janeiro de 2003): 1725–34. http://dx.doi.org/10.1016/s0731-7085(02)00514-9.
Texto completo da fonte
21
Sree Kumar, K., Yashesh N. Vaishnav e Joseph F. Weiss. "Radioprotection by antioxidant enzymes and enzyme mimetics". Pharmacology & Therapeutics 39, n.º 1-3 (janeiro de 1988): 301–9. http://dx.doi.org/10.1016/0163-7258(88)90076-9.
Texto completo da fonte
22
Mebs, D., S. Mieseler, U. Rimpau, C. Vossius, B. König e S. Benesch. "Enzymes and enzyme inhibitors from marine sponges". Toxicon 33, n.º 3 (março de 1995): 304. http://dx.doi.org/10.1016/0041-0101(95)99364-9.
Texto completo da fonte
23
O'Keefe, S. J., W. M. Bennet, A. R. Zinsmeister e M. W. Haymond. "Pancreatic enzyme synthesis and turnover in human subjects". American Journal of Physiology-Gastrointestinal and Liver Physiology 266, n.º 5 (1 de maio de 1994): G816—G821. http://dx.doi.org/10.1152/ajpgi.1994.266.5.g816.
Texto completo da fonteResumo:
Animal studies have shown that pancreatic enzyme secretion is independent of enzyme synthesis. To investigate this relationship in humans, we have coinfused 14C-labeled leucine tracer with cholecystokinin octapeptide in nine healthy adults for 4 h and measured the rate of appearance of secreted and newly labeled enzymes in the duodenum. Enzyme secretion was well maintained throughout, but newly labeled enzymes only appeared in juice between 75 and 101 min (median time, 86 min), indicating that initial secretion was dependent on the release of zymogen stores and that the median production time for new enzymes was 86 min. Between 85 and 225 min there was a curvilinear increase in the enrichment of secreted enzymes with newly synthesized enzymes, suggesting a median turnover rate of zymogen stores of 29%/h (range 12-47%/h). In conclusion, our results suggest that in healthy humans, postprandial pancreatic enzyme secretion is maintained by the export of a large stored pool and is not rate limited by enzyme synthesis, since it takes approximately 86 min for newly synthesized enzymes to take part in the digestive process.
24
Wu, Zhuofu, Linjuan Shi, Xiaoxiao Yu, Sitong Zhang e Guang Chen. "Co-Immobilization of Tri-Enzymes for the Conversion of Hydroxymethylfurfural to 2,5-Diformylfuran". Molecules 24, n.º 20 (10 de outubro de 2019): 3648. http://dx.doi.org/10.3390/molecules24203648.
Texto completo da fonteResumo:
Acting as a “green” manufacturing route, the enzyme toolbox made up of galactose oxidase, catalase, and horseradish peroxidase can achieve a satisfactory yield of 2,5-diformylfuran derived from 30 mM hydroxymethylfurfural. However, as the concentration of hydroxymethylfurfural increases, the substrate causes oxidative damage to the activity of the tri-enzyme system, and the accumulated hydrogen peroxide produced by galactose oxidase causes tri-enzyme inactivation. The cost of tri-enzymes is also very high. These problems prevent the utilization of this enzyme toolbox in practice. To address this, galactose oxidase, catalase, and horseradish peroxidase were co-immobilized into Cu3(PO4)2 nanoflowers in this study. The resulting co-immobilized tri-enzymes possessed better tolerance towards the oxidative damage caused by hydroxymethylfurfural at high concentrations, as compared to free tri-enzymes. Moreover, the 2,5-diformylfuran yield of co-immobilized tri-enzymes (95.7 ± 2.7%) was 1.06 times higher than that of separately immobilized enzymes (90.4 ± 1.9%). This result could be attributed to the boosted protective effect provided by catalase to the activity of galactose oxidase, owing to the physical proximity between them on the same support. After 30 recycles, co-immobilized tri-enzymes still achieves 86% of the initial yield. Moreover, co-immobilized tri-enzymes show enhanced thermal stability compared with free tri-enzymes. This work paves the way for the production of 2,5-diformylfuran from hydroxymethylfurfural via co-immobilized tri-enzymes.
25
Elnashar, Magdy M. M., e Mohamed E. Hassan. "Novel Epoxy Activated Hydrogels for Solving Lactose Intolerance". BioMed Research International 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/817985.
Texto completo da fonteResumo:
“Lactose intolerance” is a medical problem for almost 70% of the world population. Milk and dairy products contain 5–10% w/v lactose. Hydrolysis of lactose by immobilized lactase is an industrial solution. In this work, we succeeded to increase the lactase loading capacity to more than 3-fold to 36.3 U/g gel using epoxy activated hydrogels compared to 11 U/g gel using aldehyde activated carrageenan. The hydrogel’s mode of interaction was proven by FTIR, DSC, and TGA. The high activity of the epoxy group was regarded to its ability to attach to the enzyme’s –SH, –NH, and –OH groups, whereas the aldehyde group could only bind to the enzyme’s –NH2group. The optimum conditions for immobilization such as epoxy chain length and enzyme concentration have been studied. Furthermore, the optimum enzyme conditions were also deliberated and showed better stability for the immobilized enzyme and the Michaelis constants,KmandVmax, were doubled. Results revealed also that both free and immobilized enzymes reached their maximum rate of lactose conversion after 2 h, albeit, the aldehyde activated hydrogel could only reach 63% of the free enzyme. In brief, the epoxy activated hydrogels are more efficient in immobilizing more enzymes than the aldehyde activated hydrogel.
26
Wang, Sheng-Wei, e Tian-Yi Wang. "Study on Antibacterial Activity and Structure of Chemically Modified Lysozyme". Molecules 28, n.º 1 (22 de dezembro de 2022): 95. http://dx.doi.org/10.3390/molecules28010095.
Texto completo da fonteResumo:
Lysozyme is a natural protein with a good bacteriostatic effect, but its poor inhibition of Gram-negative bacteria limits its development potential as a natural preservative. Therefore, the modification of natural lysozyme to expand the antimicrobial spectrum become the focus of lysozyme study. Egg white lysozyme has low cost, rich content in nature, is easy to obtain, strong stability, and high enzyme activity, so it can be applied in the modification of lysozyme. Egg white lysozyme was modified by chemical methods using organic acids. Caffeic acid and p-coumaric acid in organic acids were used as modifiers, and 1-Ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxy succinimide were used as dehydration condensation agents during modification. A certain degree of modified lysozyme was obtained through appropriate modification conditions. The antibacterial properties and structure of the obtained two organic acid-modified lysozymes were compared with natural enzymes. The results showed that compared with the native enzyme, the activity of modified lysozyme decreased, but the inhibitory effect on Gram-negative bacteria was enhanced. The minimum inhibitory concentrations of caffeic acid-modified enzyme and p-coumaric acid-modified enzyme on Escherichia coli and Pseudomonas aeruginosa were 0.5 mg/mL and 0.75 mg/mL, respectively. However, the antibacterial ability of modified lysozyme to Gram-positive bacteria was lower than that of the natural enzyme. The minimum inhibitory concentration of caffeic acid-modified enzyme and p-coumaric acid-modified enzyme to Staphylococcus aureus and Bacillus subtilis was 1.25 mg/mL. The peak fitting results of the amide-I band absorption peak in the infrared spectroscopy showed that the content of the secondary structure of the two modified enzymes obtained after modification was different from that of natural enzymes. In the study, two organic acids were used to modify egg white lysozyme, which enhanced the enzyme’s inhibition of Gram-negative bacteria, and analyzed the mechanisms for the change in the enzyme’s antibacterial ability from the perspective of the structural change of the modified enzyme, providing a new idea for lysozyme modification.
27
Dima, Lintang A. M., Andriani Rafael, Sonya T. M. Nge, Ocky K. Radjasa, Tiodor S. J. Manalu e James Ngginak. "Isolation and Selection of Extracellular Enzymes in Sponge Symbiont Bacteria (Porifera: Demospongiae) from Tablolong Beach". JURNAL PEMBELAJARAN DAN BIOLOGI NUKLEUS 9, n.º 3 (30 de novembro de 2023): 727–42. http://dx.doi.org/10.36987/jpbn.v9i3.5222.
Texto completo da fonteResumo:
Marine biota has many benefits for human life. Sponges are a species of marine biota that can be used as a producer of antimicrobial compounds. The bacteria found in sponges have an important role in the continuity of life in the sea. The symbiotic lifestyle that occurs in bacteria and sponges has the opportunity to form substitutions for the content of secondary metabolites and enzymes, especially extracellular enzymes (amylase, protease, cellulose and lipase). This study aims to determine how to isolate sponge symbiotic bacteria and identify spongy symbiotic bacteria. The method used is purposive to take sponges. Characterization of bacteria was carried out based on morphology and gram staining. Enzymatic bacterial selection was carried out by testing the activity of the amylase enzyme (soluble starch), lipase enzyme (Teen 80), protease enzyme (skim milk) and cellulose enzyme (carboxyl methyl cellulose). Data analysis was performed in a qualitative descriptive manner by measuring the clear zone in the extracellular enzyme test results. Meanwhile, other research parameters measured in this study were temperature, salinity and pH. The results showed that out of 47 isolated bacteria and 33 of them had extracellular enzymes with 10 bacteria had amylase enzymes, 27 bacteria had lipase enzymes, 2 bacteria had protease enzymes and 1 isolate had cellulose enzymes.
28
Khudhair, Saad Hussein, Melad Khalaf Mohammed e Ahmed Darweesh Jabbar. "Immobilization of lipase enzyme extracted from thermophilic Bacillus licheniformis 14T local isolate". Advancements in Life Sciences 11, n.º 2 (29 de abril de 2024): 362. http://dx.doi.org/10.62940/als.v11i2.2251.
Texto completo da fonteResumo:
Background: Currently, lipase enzymes are considered important bio-catalysts in many industries due to their unique properties in catalyzing various types of reactions in aqueous solutions. By targeting hydrocarbons in the oil, lipase enzymes contribute to the breakdown of hydrocarbons, reducing the environmental impact of oil spills and facilitating the remediation of contaminated areas.Methods: A thermostable lipase from local isolate Bacillus licheniformis 14T has been immobilized on four different supports that include the inactivated chitosan beads, activated chitosan beads with glutaraldehyde, inactivated chitosan-alginate beads, and activated chitosan-alginate beads with glutaraldehyde.Results The purified free lipase enzyme exhibited the highest enzymatic activity at 34.6 units/ml, surpassing all immobilized enzymes. Specific activity increased to 96.25 and 79.03 unit/mg protein for activated chitosan beads and activated chitosan-alginate beads, while decreasing to 52.95 and 46.05 unit/mg protein for inactivated chitosan beads and inactivated chitosan-alginate beads compared to the free enzyme. Optimal conditions for the immobilized enzyme differed, with the highest enzyme activity achieved after 60 minutes at 60°C and pH 8, reaching 48.6, 70.23, 43.12, and 61.2 units/ml on various supports, contrasting with the free enzyme's peak activity after 30 minutes at 50°C and pH 7.Conclusions: Immobilizing the lipase enzyme increases the specific activity of the immobilized enzyme on the supports of activated chitosan beads with, also the immobilization process led to a change in the optimal conditions for the activity of the immobilized enzyme compared with the optimal conditions of free enzyme.Keywords: Lipase; Bacillus licheniformis; Immobilization; Chitosan; Alginate
29
Ali, Hala M., e Ghazi M. Aziz. "Purification and characterization of amylase from local isolate Pseudomonas sp.SPH4". Journal of Biotechnology Research Center 6, n.º 1 (1 de janeiro de 2012): 69–79. http://dx.doi.org/10.24126/jobrc.2012.6.1.205.
Texto completo da fonteResumo:
The amylase produced from local isolate Pseudomonas sp. SPH4 was purified by precipitation with 30% saturation ammonium sulphate, followed by ion-exchange chromotography using DEAE-cellulose column, and Gel filtration using Sephacryl S-300 column.The two iso-enzymes (a, b) were purified to (2.83, 3.47) times in the last step with an enzymes yields of (32.36, 76.34)% respectively. Enzyme characterization of the two iso-enzymes indicated that the optimum pH for the two iso-enzymes a and b were (7, 7.5) respectively, while the optimum pH for the iso-enzymes stability were (6.5, 7) respectively. The maximum activity for iso-enzymes (a, b) appeared at 45ºC and stable for 15 min at 30-50ºC and lost approximately 50% of it's activity at rang above 75ºC. Enzyme characterization results showed that the chlorides of silver and mercury had inhibitory effect on enzyme activity, the remaining enzyme activity for the iso-enzymes (a, b) were (46.66, 36.36)% for silver ions and (41.33, 33.63)% for mercury ions at 5 mM respectively, and (28, 28.18)% for silver ions and (25.33, 19.09)% for mercury ions at 10 mM respectively. The iso-enzymes a and b were affected by chelating agent ethylene diamine tetra acetic acid (EDTA) at concentration 2mM the remaining activity (45.33, 43.63)% respectively, and 5mM the remaining activity (28, 28.18)% respectivily, and these iso-enzymes (a, b) refered to metalloenzymes. The iso-enzymes (a, b) were kept their activity when treated by reducing agent (2-mercaptoethanol) at 2 mM the remaining activity (92, 92.72)% respectively, and 5 mM the remaining activity (85.3, 89.09)% respectivily. The iso-enzymes (a, b) were kept their activity when treated by phenyl methyl sulphonyl fluoride (PMSF) at concentration 1mM the remaining activity (93.33, 90.90)% respectivily,and 5 mM the remaining activity (90.66, 87.27)% respectivily, and these indicated that these iso-enzymes didnot referred to serineamylases group.
30
Demain, Arnold L., e Sergio Sánchez. "Enzymes of industrial interest". Mexican journal of biotechnology 2, n.º 2 (1 de julho de 2017): 74–97. http://dx.doi.org/10.29267/mxjb.2017.2.2.74.
Texto completo da fonteResumo:
For many years, industrial enzymes have played an important role in the benefit of our society due to their many useful properties and a wide range of applications. They are key elements in the progress of many industries including foods, beverages, pharmaceuticals, diagnostics, therapy, personal care, animal feed, detergents, pulp and paper, textiles, leather, chemicals and biofuels. During recent decades, microbial enzymes have replaced many plant and animal enzymes. This is because microbial enzymes are widely available and produced economically in short fermentations and inexpensive media. Screening is simple, and strain improvement for increased production has been very successful. The advances in recombinant DNA technology have had a major effect on production levels of enzymes and represent a way to overproduce industrially important microbial, plant and animal enzymes. It has been calculated that 50-60% of the world enzyme market is supplied with recombinant enzymes. Molecular methods, including genomics and metagenomics, are being used for the discovery of new enzymes from microbes. Also, directed evolution has allowed the design of enzyme specificities and better performance.
31
Su, Xiaoyun, Yejun Han, Dylan Dodd, Young Hwan Moon, Shosuke Yoshida, Roderick I. Mackie e Isaac K. O. Cann. "Reconstitution of a Thermostable Xylan-Degrading Enzyme Mixture from the Bacterium Caldicellulosiruptor bescii". Applied and Environmental Microbiology 79, n.º 5 (21 de dezembro de 2012): 1481–90. http://dx.doi.org/10.1128/aem.03265-12.
Texto completo da fonteResumo:
ABSTRACTXylose, the major constituent of xylans, as well as the side chain sugars, such as arabinose, can be metabolized by engineered yeasts into ethanol. Therefore, xylan-degrading enzymes that efficiently hydrolyze xylans will add value to cellulases used in hydrolysis of plant cell wall polysaccharides for conversion to biofuels. Heterogeneous xylan is a complex substrate, and it requires multiple enzymes to release its constituent sugars. However, the components of xylan-degrading enzymes are often individually characterized, leading to a dearth of research that analyzes synergistic actions of the components of xylan-degrading enzymes. In the present report, six genes predicted to encode components of the xylan-degrading enzymes of the thermophilic bacteriumCaldicellulosiruptor besciiwere expressed inEscherichia coli, and the recombinant proteins were investigated as individual enzymes and also as a xylan-degrading enzyme cocktail. Most of the component enzymes of the xylan-degrading enzyme mixture had similar optimal pH (5.5 to ∼6.5) and temperature (75 to ∼90°C), and this facilitated their investigation as an enzyme cocktail for deconstruction of xylans. The core enzymes (two endoxylanases and a β-xylosidase) exhibited high turnover numbers during catalysis, with the two endoxylanases yielding estimatedkcatvalues of ∼8,000 and ∼4,500 s−1, respectively, on soluble wheat arabinoxylan. Addition of side chain-cleaving enzymes to the core enzymes increased depolymerization of a more complex model substrate, oat spelt xylan. TheC. besciixylan-degrading enzyme mixture effectively hydrolyzes xylan at 65 to 80°C and can serve as a basal mixture for deconstruction of xylans in bioenergy feedstock at high temperatures.
32
Rinaldo, Serena, Giorgio Giardina, Nicoletta Castiglione, Valentina Stelitano e Francesca Cutruzzolà. "The catalytic mechanism of Pseudomonas aeruginosa cd1 nitrite reductase". Biochemical Society Transactions 39, n.º 1 (19 de janeiro de 2011): 195–200. http://dx.doi.org/10.1042/bst0390195.
Texto completo da fonteResumo:
The cd1 NiRs (nitrite reductases) are enzymes catalysing the reduction of nitrite to NO (nitric oxide) in the bacterial energy conversion denitrification process. These enzymes contain two distinct redox centres: one covalently bound c-haem, which is reduced by external electron donors, and another peculiar porphyrin, the d1-haem (3,8-dioxo-17-acrylate-porphyrindione), where nitrite is reduced to NO. In the present paper, we summarize the most recent results on the mechanism of nitrite reduction by the cd1 NiR from Pseudomonas aeruginosa. We discuss the essential catalytic features of this enzyme, with special attention to the allosteric regulation of the enzyme's activity and to the mechanism employed to avoid product inhibition, i.e. trapping of the active-site reduced haem by the product NO. These results shed light on the reactivity of cd1 NiRs and assign a central role to the unique d1-haem, present only in this class of enzymes.
33
Daris, Ummi Syahda, Ummi Halimah Rahmatika e Angel Kurnilah Fitri. "The potential of plant protease enzymes as rennet alternatives for developing halal cheese product: A review". Journal of Halal Science and Research 5, n.º 1 (21 de fevereiro de 2024): 60–70. http://dx.doi.org/10.12928/jhsr.v5i1.9524.
Texto completo da fonteResumo:
Cheese, a derivative of dairy products made using the enzyme rennet, has received full attention because of the critical point for halalness from the milk coagulation process, which uses the rennet enzyme. Rennet enzymes can be obtained from the stomachs of animals such as cows, pigs, and goats, and they can also be produced from microbes. This very high risk of haram sources or unclean contamination has led to the development of cheese products using plant protease enzymes as a substitute for rennet enzymes. This study aims to highlight plant protease enzymes, characterize the enzymes produced, characterize cheese produced, and the potential of plant protease enzymes in replacing Rennet. Plants that have protease enzymes, such as noni, papaya, pineapple, red ginger, strawberries, pears, biduri, moringa, kiwi, tamarillo, and many other plants, have the potential to replace the rennet enzyme in making cheese. Thus, the doubts (mashbooh) arising from making cheese can be avoided by developing products from raw materials with guaranteed halal quality. Plant ingredients that can replace the rennet enzyme in making cheese are many and varied, for example, noni, papaya, moringa, bidi, pineapple, red ginger, kiwi, tamarillo, pears, Balanites aegyptiaca, strawberries, and many more. Doubtless, the problem of making cheese with Rennet can be avoided by developing cheese products from raw materials guaranteed to be halal. Limitations to plant protease enzymes on cheese production only apply to soft cheese, while it is difficult to produce hard cheese from plant enzymes.
34
Liu, Ziyi, e Stephen R. Smith. "Cross-Linked Enzyme Aggregate (CLEA) Preparation from Waste Activated Sludge". Microorganisms 11, n.º 8 (27 de julho de 2023): 1902. http://dx.doi.org/10.3390/microorganisms11081902.
Texto completo da fonteResumo:
Enzymes are used extensively as industrial bio-catalysts in various manufacturing and processing sectors. However, commercial enzymes are expensive in part due to the high cost of the nutrient medium for the biomass culture. Activated sludge (AS) is a waste product of biological wastewater treatment and consists of microbial biomass that degrades organic matter by producing substantial quantities of hydrolytic enzymes. Recovering enzymes from AS therefore offers a potential alternative to conventional production techniques. A carrier-free, cross-linked enzyme aggregate (CLEA) was produced from crude AS enzyme extract for the first time. A major advantage of the CLEA is the combined immobilization, purification, and stabilization of the crude enzymes into a single step, thereby avoiding large amounts of inert carriers in the final enzyme product. The AS CLEA contained a variety of hydrolytic enzymes and demonstrated high potential for the bio-conversion of complex organic substrates.
35
R, Kumaravelrajan, Swetha M e Suba V. "Characterization of Immobilized β-Amylase Enzyme Isolated from Sweet Potato and prepared by Entrapment Method". International Journal of Pharmaceutical Sciences and Nanotechnology(IJPSN) 15, n.º 6 (16 de dezembro de 2022): 6196–203. http://dx.doi.org/10.37285/ijpsn.2022.15.6.2.
Texto completo da fonteResumo:
Aim: This study attempted to isolate β-amylase from sweet potato and enzyme immobilized by encapsulation method, and characterized with various parameters.
Methods: The enzyme β-amylase was isolated with phosphate-buffered saline and purified by centrifugation with ammonium sulfate. The purified enzyme was immobilized on chitosan (0.25 g) and sodium alginate (0.25 g) polymers by entrapment method in the presence of calcium chloride (0.5 M). The immobilized enzyme was characterized by a starch hydrolysis test, the optimal pH and temperature were studied and the stability of the immobilized enzyme was also determined. SEM analysis was performed and Vm and Km were also found.
Results: The starch hydrolysis test showed positive results on the starch agar plates for immobilized enzymes. The thermal inactivation showed a severe loss in the activity of the free enzymes (49.3 %) while the temperature profile of the immobilized enzymes was much broader (84.55 %) at higher temperatures (80° C). The optimal pH and stability indicated that the immobilized enzyme has higher stability in the pH range of 5-8. The Km and Vmax value of free and immobilized enzyme was 7.67 mmol, 21.15 µmol (R2 0.8880), and 4.72 mmol,16.79 µmol (R2 0.8446) respectively. The storage of free and immobilized enzymes for one month showed that 83.5 % and 40 % of free enzymes and 11.6 % and 8.6 % of immobilized enzymes lost activity at 25° C and 4° C, respectively. SEM analysis shows the smooth, porous surface.
Conclusion: Immobilized enzymes (natural polymers) exhibit higher thermal stability the optimal pH and stability indicate immobilized enzyme has higher stability in the pH range of 5-8, and achieves a relative activity of 69.7 %. After 6 uses, the reuse efficiency of the immobilized enzyme decreased from 99.8 % to 52.3 %. The storage of the immobilized enzyme showed much higher stability than the found-free enzyme.
36
Almulaiky, Yaaser Q., J. Alkabli e Reda M. El-Shishtawy. "Sustainable Immobilization of β-Glucosidase onto Silver Ions and AgNPs-Loaded Acrylic Fabric with Enhanced Stability and Reusability". Polymers 15, n.º 22 (9 de novembro de 2023): 4361. http://dx.doi.org/10.3390/polym15224361.
Texto completo da fonteResumo:
Modified polymer design has attracted significant attention for enzyme immobilization, offering promising applications. In this study, amine-terminated polymers were synthesized by incorporating functional groups into polyacrylonitrile using hexamethylenediamine. This work highlights the successful enzyme immobilization strategy using modified polymers, offering improved stability and expanded operational conditions for potential biotechnological applications. The resulting amino groups were utilized to capture silver ions, which were subsequently converted to silver nanoparticles (AgNPs). The obtained materials, AgNPs@TA-HMDA (acrylic textiles coated silver nanoparticles AgNPs) and Ag(I)@TA-HMDA (acrylic textiles coated with Ag ion) were employed as supports for β-glucosidase enzyme immobilization. The highest immobilization yields (IY%) were achieved with AgNPs@TA-HMDA at 92%, followed by Ag(I)@TA-HMDA at 79.8%, resulting in activity yields (AY%) of 81% and 73%, respectively. Characterization techniques such as FTIR, FE-SEM, EDX, TG/DTG, DSC, and zeta potential were employed to investigate the structural composition, surface morphologies, elemental composition, thermal properties, and surface charge of the support materials. After 15 reuses, the preservation percentages decreased to 76% for AgNPs@TA-HMDA/β-Glu and 65% for Ag(I)@TA-HMDA/β-Glu. Storage stability revealed that the decrease in activity for the immobilized enzymes was smaller than the free enzyme. The optimal pH for the immobilized enzymes was broader (pH 5.5 to 6.5) compared to the free enzyme (pH 5.0), and the optimal temperature for the immobilized enzymes was 60 °C, slightly higher than the free enzyme’s optimal temperature of 50 °C. The kinetic analysis showed a slight increase in Michaelis constant (Km) values for the immobilized enzymes and a decrease in maximum velocity (Vmax), turnover number (Kcat), and specificity constant (Kcat/Km) values compared to the free enzyme. Through extensive characterization, we gained valuable insights into the structural composition and properties of the modified polymer supports. This research significantly contributes to the development of efficient biotechnological processes by advancing the field of enzyme immobilization and offering valuable knowledge for its potential applications.
37
Jovov, B., N. K. Wills, P. J. Donaldson e S. A. Lewis. "Vectorial secretion of a kallikrein-like enzyme by cultured renal cells. I. General properties". American Journal of Physiology-Cell Physiology 259, n.º 6 (1 de dezembro de 1990): C869—C882. http://dx.doi.org/10.1152/ajpcell.1990.259.6.c869.
Texto completo da fonteResumo:
Urinary kallikreins are proteolytic enzymes known to be secreted by distal nephron tubules. In this study, we demonstrate (using the chromogenic tripeptide substrate S 2266) that the renal cell line A6 from Xenopus laevis secretes a kallikrein-like enzyme. Secretion is present only when the cells are grown on filters, and enzyme is secreted only into the apical membrane bathing solution. Enzyme secretion consists of two components, one soybean trypsin inhibitor (SBTI) sensitive (SSBTI) and the other insensitive to SBTI (ISBTI). Both enzymes were inhibited by aprotinin, a kallikrein-like enzyme inhibitor. Using a bioassay, only the ISBTI enzyme produced a hypotensive effect on blood pressure and is thus a kallikrein-like enzyme. The apical membrane of cells grown on filters contains both enzyme species, whereas the basolateral membrane contains only the ISBTI (kallikrein-like) enzyme. Both enzymes were present in the apical membrane of cells grown on plastic. Initiation of enzyme secretion occurred after the cells formed electrically tight monolayers and the increase in membrane activity always preceded enzyme secretion. Using an irreversible inhibitor of the apical membrane-bound enzymes, the turnover rate for the SSBTI and ISBTI enzymes (cells on filters) was 3 and 7 h, respectively. Because the recovery of enzyme secretion was proportional to the recovery of membrane-bound enzyme activities, this suggests that enzyme secretion is due to the release of membrane-bound enzyme.
38
Suresh, Harsha Garadi, Aline Xavier da Silveira dos Santos, Wanda Kukulski, Jens Tyedmers, Howard Riezman, Bernd Bukau e Axel Mogk. "Prolonged starvation drives reversible sequestration of lipid biosynthetic enzymes and organelle reorganization in Saccharomyces cerevisiae". Molecular Biology of the Cell 26, n.º 9 (maio de 2015): 1601–15. http://dx.doi.org/10.1091/mbc.e14-11-1559.
Texto completo da fonteResumo:
Cells adapt to changing nutrient availability by modulating a variety of processes, including the spatial sequestration of enzymes, the physiological significance of which remains controversial. These enzyme deposits are claimed to represent aggregates of misfolded proteins, protein storage, or complexes with superior enzymatic activity. We monitored spatial distribution of lipid biosynthetic enzymes upon glucose depletion in Saccharomyces cerevisiae. Several different cytosolic-, endoplasmic reticulum–, and mitochondria-localized lipid biosynthetic enzymes sequester into distinct foci. Using the key enzyme fatty acid synthetase (FAS) as a model, we show that FAS foci represent active enzyme assemblies. Upon starvation, phospholipid synthesis remains active, although with some alterations, implying that other foci-forming lipid biosynthetic enzymes might retain activity as well. Thus sequestration may restrict enzymes' access to one another and their substrates, modulating metabolic flux. Enzyme sequestrations coincide with reversible drastic mitochondrial reorganization and concomitant loss of endoplasmic reticulum–mitochondria encounter structures and vacuole and mitochondria patch organelle contact sites that are reflected in qualitative and quantitative changes in phospholipid profiles. This highlights a novel mechanism that regulates lipid homeostasis without profoundly affecting the activity status of involved enzymes such that, upon entry into favorable growth conditions, cells can quickly alter lipid flux by relocalizing their enzymes.
39
Gupta, Supriya, Aiman Tanveer, Shruti Dwivedi, Kanchan Yadav, Vivek Kumar Morya e Dinesh Yadav. "Isolation and Characterization of Aeromonas taiwanensis Strain for Simultaneous Production of Cellulase, Amylase, Pectinase, and Protease Enzymes". Biosciences Biotechnology Research Asia 21, n.º 2 (1 de julho de 2024): 655–70. http://dx.doi.org/10.13005/bbra/3254.
Texto completo da fonteResumo:
ABSTRACT: A study was conducted to discover a novel microorganism capable of producing multiple enzymes with industrial applications. Bacterial isolates were screened from a soil sample collected from a wood-decaying area, and their ability to produce various enzymes of industrial significance was evaluated. Among the 100 screened bacterial isolates, the strain GCEL-BGb85 was identified as Aeromonas taiwanensis through 16s RNA sequencing. Further screening revealed that this microorganism could produce cellulase, pectinase, protease, and amylase enzymes. The strain was set up for enzyme production, and the enzyme activity levels for cellulase, amylase, pectinase, and protease were 0.071, 0.201, 0.202, and 0.152 U/ml, respectively. All four enzymes demonstrated optimal activity at 40°C with a distinct pH. The zymogram analysis confirmed the presence of these enzymes in the isolated bacterial strain. As all the enzymes isolated from this strain are industrially significant, the application of the cell-free extract containing all these enzymes was evaluated at a laboratory scale for its potential use in industrial applications. The enzyme cocktail demonstrated its utility in the retting of fibers, effectively removing blood and egg yolk stains and extracting fruit juices and oil. The enzyme extract was also found to be useful in sustainable waste management.
40
Ainscough, R. J., J. M. McGree, M. J. Callaghan e R. E. Speight. "Effective incorporation of xylanase and phytase in lick blocks for grazing livestock". Animal Production Science 59, n.º 9 (2019): 1762. http://dx.doi.org/10.1071/an18424.
Texto completo da fonteResumo:
The addition of feed enzymes to livestock diets has contributed to significant increases in productivity over recent decades. The use of enzymes has been the most common in systems where enzyme delivery and diets can be easily managed, such as for poultry and pigs. Lick blocks supplement the forage diets of ruminants with nitrogen and minerals but not enzymes, due in part to concerns that block manufacturing temperatures would lead to unacceptable levels of enzyme degradation. The nutritional value of low quality pasture could be improved using enzyme supplemented lick blocks if enzymes remain active at the high lick block manufacturing temperatures. The aim of this study was to determine the extent of xylanase and phytase activity survival when exposed to the production of hot poured lick blocks. Lick block formulations and methods of manufacturing vary, so two enzyme containing molasses-based lick blocks were produced, one at 60°C and another at 100°C. The results showed that both the xylanase and phytase enzymes have high levels of survival at 60°C. In the 100°C lick block, the phytase displayed a half-life of ~10 min, whereas the xylanase retained 90% of the original activity after 30 min of exposure. The inherent thermostability of the enzymes were critical factors for enzyme survival and the enzymes were more stable in the lick blocks than in solution. The results indicate that it should be possible to add enzymes to lick blocks manufactured at elevated temperatures to enhance low quality pasture and thereby aid ruminant digestion and production.
41
Liu, Sun, Cui e Ding. "Molecular Modification of Fluoroquinolone-Biodegrading Enzymes Based on Molecular Docking and Homology Modelling". International Journal of Environmental Research and Public Health 16, n.º 18 (13 de setembro de 2019): 3407. http://dx.doi.org/10.3390/ijerph16183407.
Texto completo da fonteResumo:
To improve the biodegradation efficiency of fluoroquinolone antibiotics during sewage treatment, fluoroquinolone aerobic, anaerobic and facultative degrading enzymes for fluoroquinolone degradation were modified by molecular docking and homology modelling. First, amino acid residues of the binding sites of degrading enzymes for the target fluoroquinolones ciprofloxacin (CIP), norfloxacin (NOR) and ofloxacin (OFL) were analysed by the molecular docking method. The hydrophobic amino acid residues within 5 Å of the target fluoroquinolone molecules were selected as the modification sites. The hydrophobic amino acid residues at the modified sites were replaced by the hydrophilic amino acid residues, and 150 amino acid sequence modification schemes of the degrading enzymes were designed. Subsequently, a reconstruction scheme of the degrading enzyme amino acid sequence reconstruction scheme was submitted to the SWISS-MODEL server and a selected homology modelling method was used to build a new structure of the degrading enzyme. At the same time, the binding affinities between the novel degrading enzymes and the target fluoroquinolones (represented by the docking scoring function) were evaluated by the molecular docking method. It was found that the novel enzymes can simultaneously improve the binding affinities for the three target fluoroquinolones, and the degradation ability of the six modification schemes was increased by more than 50% at the same time. Among the novel enzymes, the affinity effect of the novel anaerobic enzyme (6-1) with CIP, NOR and OFL was significantly increased, with increases of 129.24%, 165.06% and 169.59%, respectively, followed by the facultative enzyme and aerobic enzyme. In addition, the designed degrading enzymes had certain selectivity for the degradation of the target quinolone. Among the novel enzymes, the binding affinities of the novel anaerobic enzyme (6-3) and CIP, the novel aerobic enzyme (3-6) and NOR, and the novel facultative enzyme (13-6) and OFL were increased by 149.71%, 178.57% and 297.12% respectively. Calculations using the Gaussian09 software revealed that the degradation reaction barrier of the novel degrading enzyme (7-1) and CIP NOR and OFL decreased by 37.65 kcal·mol−1, 6.28 kcal·mol−1 and 6.28 kcal·mol−1, respectively, which would result in efficient degradation of the target fluoroquinolone molecules. By analysing the binding affinity of the degrading enzymes before and after the modification with methanol, it was further speculated that the degradation effect of the modified aerobic degrading enzymes on organic matter was lower than that before the modification, and the increase or decrease in the degradation effect was less than 10%. The mechanism analysis found that the interaction between the modified amino acid residues of the degrading enzymes and the fluoroquinolone molecules increased. The average distance between the amino acid residues and the fluoroquinolone molecules represented a comprehensive affinity effect, and its value was positively correlated with the degradation effect of the novel degrading enzymes.
42
SAITO, AKINOBU, e RYO HONDO. "Genome Variation among Listeria monocytogenes Isolates Derived from Epidemiologically Related Raw Milk and Other Strains". Journal of Food Protection 59, n.º 9 (1 de setembro de 1996): 998–1002. http://dx.doi.org/10.4315/0362-028x-59.9.998.
Texto completo da fonteResumo:
Listeria monocytogenes strains were examined by restriction-enzyme analysis of chromosomal DNA using a total of 18 restriction enzymes. Ten of the 6-base restriction enzymes and one 8-base restriction enzyme produced distinguishable fragments among these strains. Six strains (serotype 1/2a) recovered from raw milk suspected of the same contaminant were compared with seven epidemiologically unrelated strains (serotype 1/2a) using 10 of the 6-base restriction enzymes. The restriction enzyme patterns of the six raw milk isolates were identical to each other, but differed from those of the other strains. Restriction-enzyme analysis of the chromosomal DNA of L. monocytogenes by using the 6-base restriction enzymes may be a useful method of epidemiological analysis for listeriosis outbreaks.
43
Cowieson, A. J., M. Hruby e E. E. M. Pierson. "Evolving enzyme technology: impact on commercial poultry nutrition". Nutrition Research Reviews 19, n.º 1 (junho de 2006): 90–103. http://dx.doi.org/10.1079/nrr2006121.
Texto completo da fonteResumo:
AbstractThe use of exogenous enzymes to improve the nutritional value of poultry diets is a relatively new concept. The technology is rapidly evolving, with new enzymes, enzyme combinations, and novel applications being developed as rapidly as regulatory restrictions will allow. Most researchers in the field of poultry nutrition would consider phytase to be the last significant leap forward in terms of enzyme use in the animal feed industry. However, there is a great deal of ongoing research into the next generation of enzymes with a focus on ingredient quality, predictability of response via least-square models, improvements in food safety, effect of bird age, effect of various side activities and enzyme dose, maximisation of net income and reduction in environmental pollution. It is the purpose of the present review article to summarise the current research in the area of feed enzymes for poultry and to speculate on future applications of enzymes and new enzyme technologies that may be of value to the industry in the coming years.
44
Noviandi, Idham, Fita Ridhana, Erita Erita e Nasrullah Nasrullah. "Penambahan Enzim Sawit Dalam Pakan Yang Berbeda Terhadap Performa Ayam Broiler". JIPVET: Jurnal Ilmu Peternakan dan Veteriner 3, n.º 2 (15 de dezembro de 2021): 16–22. http://dx.doi.org/10.55542/jipvet.v3i2.144.
Texto completo da fonteResumo:
Addition of Palm Enzymes in with Different Variations in Chicken Performance of Undergraduate. The purpose of this study was to determine the effect of giving palm oil enzymes to the weight gain of broiler chickens. the consumption of broiler chicken feed. To determine the administration of palm enzymes influence the increase in broiler chicken feed conversion. The design used in this study was a Completely Randomized Design (CRD), the provision of Palm Enzymes and without the provision of Palm Enzymes. By giving chicken ration given to Broiler Chicken P0: Without the addition of 0% palm enzyme (control), P1: addition of 25 ml palm enzyme + 75 commercial feed, P2: addition of 50 ml palm enzyme + 50 commercial feed P3: addition of palm enzyme 75 ml + 25 commercial feed. On the parameters of observation of body weight, feed consumption and broiler chicken feed conversion obtained during the study were best found in treatment P1: addition of 25 ml palm enzyme + 75 commercial feed. In the sidik analysis, the various effects of body weight, feed consumption and feed conversion between treatments different significantly.
45
Idham Noviandi, Fita Ridhana, Erita e Nasrullah. "Penambahan Enzim Sawit Dalam Pakan Yang Berbeda Terhadap Performa Ayam Broiler". JURNAL RISET RUMPUN ILMU HEWANI 1, n.º 1 (22 de março de 2022): 16–22. http://dx.doi.org/10.55606/jurrih.v1i1.71.
Texto completo da fonteResumo:
Addition of Palm Enzymes in with Different Variations in Chicken Performance of Undergraduate. The purpose of this study was to determine the effect of giving palm oil enzymes to the weight gain of broiler chickens. the consumption of broiler chicken feed. To determine the administration of palm enzymes influence the increase in broiler chicken feed conversion. The design used in this study was a Completely Randomized Design (CRD), the provision of Palm Enzymes and without the provision of Palm Enzymes. By giving chicken ration given to Broiler Chicken P0: Without the addition of 0% palm enzyme (control), P1: addition of 25 ml palm enzyme + 75 commercial feed, P2: addition of 50 ml palm enzyme + 50 commercial feed P3: addition of palm enzyme 75 ml + 25 commercial feed. On the parameters of observation of body weight, feed consumption and broiler chicken feed conversion obtained during the study were best found in treatment P1: addition of 25 ml palm enzyme + 75 commercial feed. In the sidik analysis, the various effects of body weight, feed consumption and feed conversion between treatments different significantly.
46
Shomar, Helena, e Gregory Bokinsky. "Towards a Synthetic Biology Toolset for Metallocluster Enzymes in Biosynthetic Pathways: What We Know and What We Need". Molecules 26, n.º 22 (17 de novembro de 2021): 6930. http://dx.doi.org/10.3390/molecules26226930.
Texto completo da fonteResumo:
Microbes are routinely engineered to synthesize high-value chemicals from renewable materials through synthetic biology and metabolic engineering. Microbial biosynthesis often relies on expression of heterologous biosynthetic pathways, i.e., enzymes transplanted from foreign organisms. Metallocluster enzymes are one of the most ubiquitous family of enzymes involved in natural product biosynthesis and are of great biotechnological importance. However, the functional expression of recombinant metallocluster enzymes in live cells is often challenging and represents a major bottleneck. The activity of metallocluster enzymes requires essential supporting pathways, involved in protein maturation, electron supply, and/or enzyme stability. Proper function of these supporting pathways involves specific protein–protein interactions that remain poorly characterized and are often overlooked by traditional synthetic biology approaches. Consequently, engineering approaches that focus on enzymatic expression and carbon flux alone often overlook the particular needs of metallocluster enzymes. This review highlights the biotechnological relevance of metallocluster enzymes and discusses novel synthetic biology strategies to advance their industrial application, with a particular focus on iron-sulfur cluster enzymes. Strategies to enable functional heterologous expression and enhance recombinant metallocluster enzyme activity in industrial hosts include: (1) optimizing specific maturation pathways; (2) improving catalytic stability; and (3) enhancing electron transfer. In addition, we suggest future directions for developing microbial cell factories that rely on metallocluster enzyme catalysis.
47
Wang, Xinglong, Kangjie Xu, Yameng Tan, Song Liu e Jingwen Zhou. "Possibilities of Using De Novo Design for Generating Diverse Functional Food Enzymes". International Journal of Molecular Sciences 24, n.º 4 (14 de fevereiro de 2023): 3827. http://dx.doi.org/10.3390/ijms24043827.
Texto completo da fonteResumo:
Food enzymes have an important role in the improvement of certain food characteristics, such as texture improvement, elimination of toxins and allergens, production of carbohydrates, enhancing flavor/appearance characteristics. Recently, along with the development of artificial meats, food enzymes have been employed to achieve more diverse functions, especially in converting non-edible biomass to delicious foods. Reported food enzyme modifications for specific applications have highlighted the significance of enzyme engineering. However, using direct evolution or rational design showed inherent limitations due to the mutation rates, which made it difficult to satisfy the stability or specific activity needs for certain applications. Generating functional enzymes using de novo design, which highly assembles naturally existing enzymes, provides potential solutions for screening desired enzymes. Here, we describe the functions and applications of food enzymes to introduce the need for food enzymes engineering. To illustrate the possibilities of using de novo design for generating diverse functional proteins, we reviewed protein modelling and de novo design methods and their implementations. The future directions for adding structural data for de novo design model training, acquiring diversified training data, and investigating the relationship between enzyme–substrate binding and activity were highlighted as challenges to overcome for the de novo design of food enzymes.
48
Isheanesu Dzambi e Rumbidzai Mangoyi. "The effects of Psidium guajava leaf extract on the production of cellulases and glucose oxidases by Aspergillus niger". GSC Advanced Research and Reviews 5, n.º 2 (30 de novembro de 2020): 118–22. http://dx.doi.org/10.30574/gscarr.2020.5.2.0109.
Texto completo da fonteResumo:
Aspergillus niger, is a filamentous fungus and producer of industrial enzymes such as glucose oxidases and cellulases. These enzymes are naturally produced by the fungus in order to digest and absorb nutrients from its environment. However, the enzyme quantities that are naturally produced are low. Thus, the aim of this study was to determine the effects of Psidum guajava leaf extract on the production of cellulases and glucose oxidases from Aspergillus niger. The leaves of Psidium guajava were extracted using absolute methanol. Aspergillus niger was then grown in the presence and absence of the extract in order to investigate the effects of extract on enzyme production by the fungus. The enzymes secreted into the broth medium were isolated by centrifugation. The supernatant which contained the secreted enzymes was used for the determination of enzyme activity. Enzyme activity was determined using the specific substrate for the specific enzyme, such as 2 % cellulose for cellulase and standard glucose solution for glucose oxidase. The results showed that the Psidium guajava leaf extract had an effect on production and activity of cellulases and glucose oxidases. From this study, it was noted that the Psidium guajava leaf extract may be used to induce the production of enzymes by Aspergillus niger and these enzymes may be of industrial use.
49
Herman, Richard Ansah, Xuan Zhu, Ellen Ayepa, Shuai You e Jun Wang. "Advances in the One-Step Approach of Polymeric Materials Using Enzymatic Techniques". Polymers 15, n.º 3 (30 de janeiro de 2023): 703. http://dx.doi.org/10.3390/polym15030703.
Texto completo da fonteResumo:
The formulation in which biochemical enzymes are administered in polymer science plays a key role in retaining their catalytic activity. The one-step synthesis of polymers with highly sequence-controlled enzymes is a strategy employed to provide enzymes with higher catalytic activity and thermostability in material sustainability. Enzyme-catalyzed chain growth polymerization reactions using activated monomers, protein–polymer complexation techniques, covalent and non-covalent interaction, and electrostatic interactions can provide means to develop formulations that maintain the stability of the enzyme during complex material processes. Multifarious applications of catalytic enzymes are usually attributed to their efficiency, pH, and temperature, thus, progressing with a critical structure-controlled synthesis of polymer materials. Due to the obvious economics of manufacturing and environmental sustainability, the green synthesis of enzyme-catalyzed materials has attracted significant interest. Several enzymes from microorganisms and plants via enzyme-mediated material synthesis have provided a viable alternative for the appropriate synthesis of polymers, effectively utilizing the one-step approach. This review analyzes more and deeper strategies and material technologies widely used in multi-enzyme cascade platforms for engineering polymer materials, as well as their potential industrial applications, to provide an update on current trends and gaps in the one-step synthesis of materials using catalytic enzymes.
50
Chang, Antje, Lisa Jeske, Sandra Ulbrich, Julia Hofmann, Julia Koblitz, Ida Schomburg, Meina Neumann-Schaal, Dieter Jahn e Dietmar Schomburg. "BRENDA, the ELIXIR core data resource in 2021: new developments and updates". Nucleic Acids Research 49, n.º D1 (19 de novembro de 2020): D498—D508. http://dx.doi.org/10.1093/nar/gkaa1025.
Texto completo da fonteResumo:
Abstract The BRENDA enzyme database (https://www.brenda-enzymes.org), established in 1987, has evolved into the main collection of functional enzyme and metabolism data. In 2018, BRENDA was selected as an ELIXIR Core Data Resource. BRENDA provides reliable data, continuous curation and updates of classified enzymes, and the integration of newly discovered enzymes. The main part contains >5 million data for ∼90 000 enzymes from ∼13 000 organisms, manually extracted from ∼157 000 primary literature references, combined with information of text and data mining, data integration, and prediction algorithms. Supplements comprise disease-related data, protein sequences, 3D structures, genome annotations, ligand information, taxonomic, bibliographic, and kinetic data. BRENDA offers an easy access to enzyme information from quick to advanced searches, text- and structured-based queries for enzyme-ligand interactions, word maps, and visualization of enzyme data. The BRENDA Pathway Maps are completely revised and updated for an enhanced interactive and intuitive usability. The new design of the Enzyme Summary Page provides an improved access to each individual enzyme. A new protein structure 3D viewer was integrated. The prediction of the intracellular localization of eukaryotic enzymes has been implemented. The new EnzymeDetector combines BRENDA enzyme annotations with protein and genome databases for the detection of eukaryotic and prokaryotic enzymes.