Littérature scientifique sur le sujet « Carbonic Anhydrase, metalloenzymes, selenium »

This study demonstrates the screening of a collection of twelve ¹⁹F-tagged metal-binding pharmacophores (MBPs) against the Zn(ii)-dependent metalloenzyme human carbonic anhydrase II (hCAII) by ¹⁹F NMR.

Carbonic anhydrases (CAs) are ubiquitous zinc metalloenzymes that catalyze the reversible dehydration of HCO3–. These enzymes are encoded by at least five distinct, evolutionarily unrelated gene families, four of which have been found among the cyanobacteria examined to date. However, the distribution and expression of these cyanobacterial α-, β-, γ-, and ∈-CAs and their homologues among species have not yet been investigated in great detail. In this study, the number, distribution, and catalytic function of known and putative CAs and CA-like proteins from a variety of freshwater and marine cyanobacteria are examined.Key words: carbonic anhydrase, carboxysome, CO2-concentrating mechanism, cyanobacteria, Prochlorococcus, Synechococcus, Synechocystis.

Carbonic anhydrases (CAs, EC 4.2.1.1) are widespread metalloenzymes in organisms in all life kingdoms, being involved in pH regulation, metabolic processes and many other physiological and pathological conditions. CA inhibitors and activators thus possess applications as pharmacological agents in the management of a range of diseases. Marine natural products have allowed the identification of some highly interesting CA inhibitors, among which are sulfonamides, phenols, polyamines, coumarins and several other miscellaneous inhibitors, which are reviewed here. Psammaplin C and some bromophenols were the most investigated classes of such marine-based inhibitors and have been used as lead molecules for developing interesting types of potent and, in some cases, isoform-selective inhibitors, with applications as antitumor agents by inhibiting human CA XII and P-glycoprotein activities. Some phenols have shown interesting bacterial and fungal β-CA inhibitory effects. Marine natural products thus constitute a gold mine for identifying novel CA inhibitors, some of which may lead to the development of novel types of pharmacological agents.

Carbonic anhydrase II is one of the forms of human α carbonic anhydrases which are ubiquitous metalloenzymes that catalyze inter-conversion of carbon dioxide and water to bicarbonate and proton, overexpression of which leads to disorders such as glaucoma. 2D and 3D Quantitative Structure Activity Relationship studies were carried out on previously synthesized series of sulfanilamide derivatives by VLife MDS software using stepwise variable, multi-linear regression and k-nearest neighbor molecular field analysis methods. 2D-QSAR model depicts contribution of halogens (such as chlorine and fluorine), methylene and oxygen atoms to inhibition of human carbonic anhydrases II activity. Using k-nearest neighbor molecular field analysis method two 3D-QSAR models (model A and B) were generated from which model A was found to be the best validated model with q2 (0.9494), pred_r2 (0.7367) and q2 _ se (0.2037). It displayed the fact that the inhibitory action of sulfanilamide derivatives against human carbonic anhydrases II is influenced by hydrophobicity and electro positivity.

X-ray and neutron crystallography are powerful techniques utilized to study the structures of biomolecules. Visualization of enzymes in complex with substrate/product and the capture of intermediate states can be related to activity to facilitate understanding of the catalytic mechanism. Subsequent analysis of small molecule binding within the enzyme active site provides insight into mechanisms of inhibition, supporting the design of novel inhibitors using a structure-guided approach. The first X-ray crystal structures were determined for small, ubiquitous enzymes such as carbonic anhydrase (CA). CAs are a family of zinc metalloenzymes that catalyze the hydration of CO2, producing HCO3- and a proton. The CA structure and ping-pong mechanism have been extensively studied and are well understood. Though the function of CA plays an important role in a variety of physiological functions, CA has also been associated with diseases such as glaucoma, edema, epilepsy, obesity, and cancer and is therefore recognized as a drug target. In this review, a brief history of crystallography and its impact on CA research is discussed.

Biomolecular recognition using a multivalent strategy has been successfully applied, this last decade on several biological targets, especially carbohydrate-processing enzymes, proteases, and phosphorylases. This strategy is based on the fact that multivalent interactions of several inhibitory binding units grafted on a presentation platform may enhance the binding affinity and selectivity. The zinc metalloenzymes carbonic anhydrases (CAs, EC 4.2.1.1) are considered as drug targets for several pathologies, and different inhibitors found clinical applications as diuretics, antiglaucoma agents, anticonvulsants, and anticancer agents/diagnostic tools. Their main drawback is related to the lack of isoform selectivity leading to serious side effects for all pathologies in which they are employed. Thus, the multivalent approach may open new opportunities in the drug design of innovative isoform-selective carbonic anhydrase inhibitors with biomedical applications.

The current review is intended to highlight recent advances in the search of new and effective modulators of the metalloenzymes Carbonic Anhydrases (CAs, EC 4.2.1.1) expressed in humans (h). CAs reversibly catalyze the CO2 hydration reaction, which is of crucial importance in the regulation of a plethora of fundamental processes at cellular level as well as in complex organisms. The first section of this review will be dedicated to compounds acting as activators of the hCAs (CAAs) and their promising effects on central nervous system affecting pathologies mainly characterized from memory and learning impairments. The second part will focus on the emerging chemical classes acting as hCA inhibitors (CAIs) and their potential use for the treatment of diseases.

We herein describe the design and synthesis of a catalytically active peptide–gold nanoparticle conjugate (Pep-Au-NP) that binds Zn(II) within its peptide monolayer and develops carbonic anhydrase activity. Specifically, a modified variant of the β-sheet forming IHIHIQI-peptide (IHQ), which forms an interstrand 3-His Zn(II)-binding site, was used as a ligand for spherical gold nanoparticles (Au-NPs). The resulting immobilized peptide maintains its ability to form β-sheets, as determined by circular dichroism (CD)-spectroscopy and, thus, maintains its ability to form Zn(II)-binding sites. The addition of Zn(II)-ions to the peptide–gold nanoparticle conjugates (Au@IHQ-NP) resulted in significant improvements in rates of ester hydrolysis of 4-nitrophenyl acetate (4-NPA) and the hydration of CO2 compared to the unconjugated peptide variants. Recycling of the catalyst revealed that Au@IHQ-NP remains intact with at least 94% of its initial activity after five rounds of CO2 hydration. The herein reported results reveal that Pep-Au-NPs are able to perform reactions catalyzed by natural metalloenzymes and open up new possibilities for the implementation of these conjugates.

Carbonic Anhydrases (CAs) are ubiquitous metalloenzymes involved in several disease conditions. There are 15 human CA (hCA) isoforms and their high homology represents a challenge for the discovery of potential drugs devoid of off-target side effects. For this reason, many synthetic and pharmacologic research efforts are underway to achieve the full pharmacological potential of CA modulators of activity. We report here a novel series of sulfanilamide derivatives containing heterocyclic carboxamide moieties which were evaluated as CA inhibitors against the physiological relevant isoforms hCA I, II, IX, and XII. Some of them showed selectivity toward isoform hCA II and hCA XII. Molecular docking was performed for some of these compounds on isoforms hCA II and XII to understand the possible interaction with the active site amino acid residues, which rationalized the reported inhibitory activity.

Carbonic anhydrases (CAs) are zinc-containing metalloenzymes that catalyze the reversible interconversion of CO2 and HCO3–. Aquatic photosynthetic organisms have evolved different forms of CO2-concentrating mechanisms to aid Rubisco in capturing CO2 from the surrounding environment. One aspect of all CO2-concentrating mechanisms is the critical roles played by various specially localized extracellular and intracellular CAs. There are three evolutionarily unrelated CA families designated α-, β-, and γ-CA. In the green alga, Chlamydomonas reinhardtii Dangeard, eight CAs have now been identified, including three α-CAs and five β-CAs. In addition, C. reinhardtii has another CA-like gene, Glp1 that is similar to known γ-CAs. To characterize these different CA isoforms, some of the CA genes have been overexpressed to determine whether the proteins have CA activity and to generate antibodies for in vivo immunolocalization. The CA proteins Cah3, Cah6, and Cah8, and the γ-CA-like protein, Glp1, have been overexpressed. Cah3, Cah6, and Cah8 have CA activity, but Glp1 does not. At least two of these proteins, Cah3 and Cah6, are localized to the chloroplast. Using immunolocalization and sequence analyses, we have determined that Cah6 is located to the chloroplast stroma and confirmed that Cah3 is localized to the chloroplast thylakoid lumen. Activity assays show that Cah3 is 100 times more sensitive to sulfonamides than Cah6. We present a model on how these two chloroplast CAs might participate in the CO2-concentrating mechanism of C. reinhardtii. Key words: carbonic anhydrase, CO2-concentrating mechanism, Chlamydomonas, immunolocalization.

Carbonic anhydrases (CAs) are zinc metalloenzymes that catalyze the reversible hydration of carbon dioxide to bicarbonate and a proton. The zinc cation in the active site of these metalloenzymes is the suggested target for small molecule inhibitors to block the endogenous CA catalysed reaction. Almost all reported CA inhibitors consist of zinc binding group (ZBG) among which the, primary sulfonamide group (-SO2NH2) is the most prominent example. Primary sulfamate (-OSO2NH2) and primary sulfamide (-NH-SO2NH2) groups also serve as zinc binding groups in CA inhibitors, however they are less represented than the primary sulfonamide group. Natural products (NPs) have proven an invaluable source of compounds for drug discovery. NPs containing primary sulfonamide (-SO2NH2) and primary sulfamate (-OSO2NH2) group are rare, while there are no NP primary sulfamides. A literature search of the Dictionary of Natural Products (DNP) database revealed only two primary sulfonamide and five primary sulfamate compounds. This project will focus on the tractable synthesis of these rare natural products, biological evaluation against CA and protein X-ray crystal structures in complex with medicinally important isozymes of CA.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Natural Sciences
Science, Environment, Engineering and Technology
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Carbonic anhydrases (CAs, EC 4.2.1.1) are a family of metalloenzymes widespread in all life kingdoms genetically classified in 7 unrelated classes (i.e. α-, β-, γ-, δ-, ζ-, η- and θ). These enzymes catalyse a very simple and essential physiological reaction, which is the carbon dioxide hydration to afford bicarbonate and protons. So far, 16 different α-CA isoforms were isolated and characterized in mammals. In many tissues CAs are concomitantly present in a variety of isoforms, which differ for their kinetics, structural properties as well as cellular and tissutal abundancy. To date, human (h) CAs are well established therapeutic targets to treat a hypertension, glaucoma. New proof-of-concepts are therapeutic applications for the treatment of epilepsy, obesity related pathologies and neuropathic pain. In the last years CA inhibitors (CAIs) were validated for the treatment of hypoxic tumors. Within the scope of this Thesis, we report new and more isoform selective modulators of CAs expressed in humans and/or in pathogenic organisms with the intent to pave the ways to the treatment of pathologies by means of innovative approaches. The current Thesis is composed of seven chapters, each one dealing with the drug design, synthesis as well as in vitro kinetic assay of new CA modulators: (i) Novel inhibitors against hCAs (ii) Potential anticancer drugs targeting primarily hCA IX and XII that are predominantly expressed in tumor cells. (iii) New class of agents for the prevention of diabetic cerebrovascular pathology (which probably target the mitochondrial isoforms hCA VA and/or hCA VB). (iv) Potential drug leads for the treatment of different neurological disorders such as antiepileptic or neuropathic pain (probably targeting hCA II and VII). (v) Agents that target various CAs from pathogenic microorganisms such as bacteria and protozoa. (vi) New activators of hCAs (vii) Kinetic activation studies on no human expressed CAs such as the α-, β-, γ-, δ-, ζ- and η-classes.

The present PhD thesis is focused on the chemical applied to synthesize new molecules as modulators of two metalloenzymes: the Carbonic Anhydrases and the Histone Deacetylases. The thesis reports the design, the preparation, the enzymatic activity and, for selected compounds, the in-vivo characterizations of the new molecules, together with the computational and crystallographic studies performed to investigate their binding modes. The Carbonic Anhydrases (CAs), one of the most efficient enzyme known in nature, evolved in eight genetically different families (α-ι). A large number of isoforms are described among the different organisms, their presence being crucial for pH regulation, secretion of electrolytes and for other essential physiological or pathological processes. For these reasons, CAs are important targets for drugs that can be used for different pathologies, providing that it could be possible to exploit the existent differences between families or isoforms to achieve a selective activity. This may not be an easy task, since the catalytic sites are well conserved, at least among the sixteen human α isoforms (I-XVI); however, variability can be found in hydrophilic and lipophilic accessory sites close to the Zn-binding domain. The Histone Deacetylases (HDACs) is an enzyme family that plays an important role in epigenetic regulation by removing the acetyl groups from the ε-amino moieties of the lysine side chains either in histones, affecting the DNA superhelix, or in non-histone proteins. Based on their homology, the 18 human HDAC isoforms were divided into four major classes (I-IV): three of them (I, II and IV) are classical, zinc-dependent HDACs whereas class III, called sirtuins, require NAD+ to function. By removing the acetyl moieties, the HDACs regulate the gene expression mediated by nuclear receptors; an altered control of this process could therefore lead to an abnormal DNA transcription and the manifestation of several diseases such as neurodegenerative pathologies, viral infections and tumors. Both the inhibition and the activation of some relevant human CA isoforms was investigated in this work of thesis. In particular, from a first series of zinc binders (series I) characterized by a chiral benzylpiperazine scaffold [N. Chiaramonte et al. Eur. J. Med. Chem. (2018), 151, 363-375], two related generations of piperazine-based Carbonic Anhydrases Inhibitors (CAIs) were developed and studied (series II-III) [N. Chiaramonte et al. Bioorg. Chem. (2019), 91, 103130]. As a result of the collaboration with Prof. Bernhard Wünsch of the University of Münster (GE), the preparation of the III series was carried out mainly in Germany. As far as Carbonic Anhydrase activators (CAAs) are concerned, structural modifications of histamine, the first CAA reported in the literature, and Clonidine led to the generation of two series (V-VI) of positive modulators of this enzyme. Additionally, the CA activation profile of a set of commercially available piperazines (series VII) was also assessed [A. Angeli et al. J. Enz. Inhib. & Med. Chem. (2018), 33,1, 303-308]. Through a poly-pharmacological approach, the inhibition of both the CAs and the HDACs was investigated by hybridizing a coumarin moiety (CA inhibitor) with the pan-HDAC inhibitor SAHA (series IV). The contemporary inhibition of these targets could be beneficial in the treatment of several diseases, among which tumors. The biological characterization of these derivatives on some human CAs is described and discussed in this thesis, while the assays against the HDACs are still ongoing.

Carbonic anhydrases (CAs, EC 4.2.1.1) are metalloenzymes and relevant drug targets with many medicinal chemistry applications. Their classes of inhibitors are in clinical use as diuretics, or drugs for the management of glaucoma, epilepsy, obesity, tumors and infectious diseases. Among the inhibitors discovered so far, coumarins constitute an interesting class. They undergo CA-catalyzed hydrolysis and act as “prodrug inhibitors”, forming 2-hydroxy-cinnamic acids, which bind at the entrance of the enzyme active site, which has a relevant variability of amino acid residues among the different CA isoforms present in mammals, humans included. Coumarins act as isoform-selective CA inhibitors against pharmacologically relevant enzymes, such as the tumor-associated CA IX and XII. Coumarins present as metabolites in many species of bacteria, fungi, plants and ascidians showed relevant CA inhibitory properties and were used as leads for obtaining synthetic derivatives with enhanced enzyme inhibitory action belonging to a variety of classes, such as polysubstituted coumarins on both rings, thiocoumarins, thioxocoumarins, sulfocoumarins, etc.<br>

The field of bioinorganic chemistry has grown tremendously in the past 25 years. Much of the work is concerned with establishing the coordination site, ligand geometry and metal oxidation state in biologically active systems. The field also extends to the preparation and characterization of simpler model complexes that mimic the spectroscopic properties and perhaps some of the reactivity of the biological system. Much of this characterization work must precede meaningful mechanistic studies. Williams has provided an interesting overview of metal ions in biology from an inorganic perspective. There are several early review series and specialized journals devoted to the subject, and a recent issue of Chemical Reviews is devoted to the area. There also are several books covering general aspects of the subject. The field is so large and the systems are so individualistic that it is necessary, for the purposes of a text such as this, to choose a few sample systems as illustrative of the mechanistic achievements and problems. Studies of bioinorganic systems inevitably use some terminology from biochemistry which may be unfamiliar to an inorganic chemist. The examples in this Chapter are all metalloenzymes which catalyze some process. Clearly they contain a metal, but there are other components of an enzyme, and terms used to describe these are summarized as follows: An apoenzyme is a polypeptide whose composition, peptide sequence and structure depend on the biological source of the metalloenzyme. Typically, the molar mass of the polypeptide is in the range of 1.5-5xl05 daltons. The polypeptide is folded into coils and sheets whose shape is determined by electrostatics and hydrogen bonding. These terms designate the same type of component, but one or the other is used more commonly for a particular system. This is a nonprotein component which binds to the apoenzyme to produce the active catalyst. It is not covalently bonded to the apoenzyme and can be removed by relatively mild denaturation of the polypeptide. Common bioinorganic examples are coenzyme B12, discussed in Section 8.3, and Zn(II) in carbonic anhydrase, discussed in Section 8.4. A prosthetic group is analogous to a coenzyme except that a prosthetic group is believed to be covalently bonded to the apoenzyme.