Academic literature on the topic 'Mo/Cu cofactor'

Cu is an essential cofactor for at least twelve mammalian enzymes including dopamine β-mono-oxygenase (DBM), which converts dopamine (DA) to noradrenaline (NA). Previous studies reported that certain Cu-deficient (Cu−) rat tissues have lower NA and higher DA than Cu-adequate (Cu+) tissues, suggesting that DBM function was impaired. However, in vitro studies suggested that DBM activity is higher in Cu− tissue. Experiments were conducted on adrenal glands (AG), medulla oblongata/pons (MO), vas deferens (VD) and heart (HT) from a single rat experiment to provide data to help clarify this puzzling contradiction. In vitro DBM activity assays showed Cu− samples had significantly higher activity than Cu+ samples in both AG and MO, but not VD. Activity data were confirmed by Western immunoblots. Quantitative real-time PCR demonstrated higher DBM mRNA in Cu− tissues but unaltered levels of several other cuproenzymes and Cu-binding proteins. Previous pharmacological data implied that high DBM was associated with low NA. HPLC analyses confirmed that NA and DA levels in Cu− MO, VD and HT were significantly lower and higher, respectively, than in Cu+ tissues. However, the NA content of AG was not statistically lower. Furthermore there was no correlation between higher DBM mRNA and lower NA in four Cu−tissues. Adequate dietary Cu is essential to support DBM function in vivo but additional studies are needed to determine the mechanism for increased DBM transcription associated with Cu deficiency.

Copper (Cu) is an essential element for cereals, playing important roles as a cofactor of several enzymes. Copper and four other metals (Fe, Mn, Zn and Mo) taken up by roots are efficiently delivered to the shoots via xylem and phloem. Here we investigated the concentrations of Cu, Fe, Mn, Zn and Mo in the xylem and phloem saps as well as in tissues of rice (Oryza sativa L.) seedlings when they were grown under different Cu levels in culture solution. Although the Cu concentrations in the roots and the Mn concentrations in the mature shoot tissues were increased with the increase of the Cu level in the culture solution, the concentrations of Cu and the other four metals in the xylem and phloem saps and the Cu contents in the shoot tissues were only slightly affected by moderate increases in the Cu medium level. The results of our analyses using membrane filtration, size-exclusion chromatography and electrospray ionisation time-of-flight mass spectrometry indicate that Cu in the xylem sap is dominantly complexed by 2′-deoxymugineic acid, whereas Cu in the phloem sap is bound to several compounds, i.e. nicotianamine, histidine and other >3-kDa compounds.

Cyanobacteria are photoautotrophic microorganisms present in almost all ecologically niches on Earth. They exist as single-cell or filamentous forms and the latter often contain specialized cells for N2 fixation known as heterocysts. Heterocysts arise from photosynthetic active vegetative cells by multiple morphological and physiological rearrangements including the absence of O2 evolution and CO2 fixation. The key function of this cell type is carried out by the metalloprotein complex known as nitrogenase. Additionally, many other important processes in heterocysts also depend on metalloproteins. This leads to a high metal demand exceeding the one of other bacteria in content and concentration during heterocyst development and in mature heterocysts. This review provides an overview on the current knowledge of the transition metals and metalloproteins required by heterocysts in heterocyst-forming cyanobacteria. It discusses the molecular, physiological, and physicochemical properties of metalloproteins involved in N2 fixation, H2 metabolism, electron transport chains, oxidative stress management, storage, energy metabolism, and metabolic networks in the diazotrophic filament. This provides a detailed and comprehensive picture on the heterocyst demands for Fe, Cu, Mo, Ni, Mn, V, and Zn as cofactors for metalloproteins and highlights the importance of such metalloproteins for the biology of cyanobacterial heterocysts.

Denitrification is a distinct means of energy conservation, making use of N oxides as terminal electron acceptors for cellular bioenergetics under anaerobic, microaerophilic, and occasionally aerobic conditions. The process is an essential branch of the global N cycle, reversing dinitrogen fixation, and is associated with chemolithotrophic, phototrophic, diazotrophic, or organotrophic metabolism but generally not with obligately anaerobic life. Discovered more than a century ago and believed to be exclusively a bacterial trait, denitrification has now been found in halophilic and hyperthermophilic archaea and in the mitochondria of fungi, raising evolutionarily intriguing vistas. Important advances in the biochemical characterization of denitrification and the underlying genetics have been achieved with Pseudomonas stutzeri, Pseudomonas aeruginosa, Paracoccus denitrificans, Ralstonia eutropha, and Rhodobacter sphaeroides. Pseudomonads represent one of the largest assemblies of the denitrifying bacteria within a single genus, favoring their use as model organisms. Around 50 genes are required within a single bacterium to encode the core structures of the denitrification apparatus. Much of the denitrification process of gram-negative bacteria has been found confined to the periplasm, whereas the topology and enzymology of the gram-positive bacteria are less well established. The activation and enzymatic transformation of N oxides is based on the redox chemistry of Fe, Cu, and Mo. Biochemical breakthroughs have included the X-ray structures of the two types of respiratory nitrite reductases and the isolation of the novel enzymes nitric oxide reductase and nitrous oxide reductase, as well as their structural characterization by indirect spectroscopic means. This revealed unexpected relationships among denitrification enzymes and respiratory oxygen reductases. Denitrification is intimately related to fundamental cellular processes that include primary and secondary transport, protein translocation, cytochrome c biogenesis, anaerobic gene regulation, metalloprotein assembly, and the biosynthesis of the cofactors molybdopterin and heme D1. An important class of regulators for the anaerobic expression of the denitrification apparatus are transcription factors of the greater FNR family. Nitrate and nitric oxide, in addition to being respiratory substrates, have been identified as signaling molecules for the induction of distinct N oxide-metabolizing enzymes.