Xanthine oxidase is a form of xanthine oxidoreductase, a type of enzyme that generates reactive oxygen species. These enzymes catalyze the oxidation of hypoxanthine to xanthine and can further catalyze the oxidation of xanthine to uric acid. These enzymes play an important role in the catabolism of purines in some species, including humans.
Rieske proteins are iron–sulfur protein (ISP) components of cytochrome bc1 complexes and cytochrome b6f complexes and are responsible for electron transfer in some biological systems. John S. Rieske and co-workers first discovered the protein and in 1964 isolated an acetylated form of the bovine mitochondrial protein. In 1979 Trumpower's lab isolated the "oxidation factor" from bovine mitochondria and showed it was a reconstitutively-active form of the Rieske iron-sulfur protein
It is a unique [2Fe-2S] cluster in that one of the two Fe atoms is coordinated by two histidine residues rather than two cysteine residues. They have since been found in plants, animals, and bacteria with widely ranging electron reduction potentials from -150 to +400 mV.
Xanthinuria, also known as xanthine oxidase deficiency, is a rare genetic disorder causing the accumulation of xanthine. It is caused by a deficiency of the enzyme xanthine oxidase.
DMSO reductase is a molybdenum-containing enzyme that catalyzes reduction of dimethyl sulfoxide (DMSO) to dimethyl sulfide (DMS). This enzyme serves as the terminal reductase under anaerobic conditions in some bacteria, with DMSO being the terminal electron acceptor. During the course of the reaction, the oxygen atom in DMSO is transferred to molybdenum, and then reduced to water.
Molybdopterins are a class of cofactors found in most molybdenum-containing and all tungsten-containing enzymes. Synonyms for molybdopterin are: MPT and pyranopterin-dithiolate. The nomenclature for this biomolecule can be confusing: Molybdopterin itself contains no molybdenum; rather, this is the name of the ligand that will bind the active metal. After molybdopterin is eventually complexed with molybdenum, the complete ligand is usually called molybdenum cofactor.
Sulfite oxidase is an enzyme in the mitochondria of all eukaryotes, with exception of the yeasts. It oxidizes sulfite to sulfate and, via cytochrome c, transfers the electrons produced to the electron transport chain, allowing generation of ATP in oxidative phosphorylation. This is the last step in the metabolism of sulfur-containing compounds and the sulfate is excreted.
Formate dehydrogenases are a set of enzymes that catalyse the oxidation of formate to carbon dioxide, donating the electrons to a second substrate, such as NAD+ in formate:NAD+ oxidoreductase (EC 1.17.1.9) or to a cytochrome in formate:ferricytochrome-b1 oxidoreductase (EC 1.2.2.1). This family of enzymes has attracted attention as inspiration or guidance on methods for the carbon dioxide fixation, relevant to global warming.
Xanthine dehydrogenase, also known as XDH, is a protein that, in humans, is encoded by the XDH gene.
Arsenate reductase (donor) (EC 1.20.99.1) is an enzyme that catalyzes the chemical reaction
Arsenate reductase (glutaredoxin) (EC 1.20.4.1) is an enzyme that catalyzes the chemical reaction
In enzymology, an ethylbenzene hydroxylase (EC 1.17.99.2) is an enzyme that catalyzes the chemical reaction
In enzymology, a NADH peroxidase (EC 1.11.1.1) is an enzyme that catalyzes the chemical reaction
Molybdopterin synthase (EC 2.8.1.12, MPT synthase) is an enzyme required to synthesize molybdopterin (MPT) from precursor Z (now known as cyclic pyranopterin monophosphate). Molydopterin is subsequently complexed with molybdenum to form molybdenum cofactor (MoCo). MPT synthase catalyses the following chemical reaction:
The aldehyde oxidase and xanthine dehydrogenase, a/b hammerhead domain is an evolutionary conserved protein domain.
Aralkylamine dehydrogenase (azurin) (EC 1.4.9.2, aromatic amine dehydrogenase, arylamine dehydrogenase, tyramine dehydrogenase) is an enzyme with the systematic name aralkylamine:azurin oxidoreductase (deaminating). This enzyme catalyses the following chemical reaction:
Caffeine dehydrogenase, commonly referred to in scientific literature as caffeine oxidase, is an enzyme with the systematic name caffeine:ubiquinone oxidoreductase. The enzyme is most well known for its ability to directly oxidize caffeine, a type of methylxanthine, to trimethyluric acid. Caffeine dehydrogenase can be found in bacterium Pseudomonas sp. CBB1 and in several species within the genera Alcaligenes, Rhodococcus, and Klebsiella.
Arsenate reductase (cytochrome c) (EC 1.20.2.1, arsenite oxidase) is an enzyme with systematic name arsenite:cytochrome c oxidoreductase. This enzyme catalyses the following chemical reaction
Arsenate-reducing bacteria are bacteria which reduce arsenates. Arsenate-reducing bacteria are ubiquitous in arsenic-contaminated groundwater (aqueous environment). Arsenates are salts or esters of arsenic acid (H3AsO4), consisting of the ion AsO43−. They are moderate oxidizers that can be reduced to arsenites and to arsine. Arsenate can serve as a respiratory electron acceptor for oxidation of organic substrates and H2S or H2. Arsenates occur naturally in minerals such as adamite, alarsite, legrandite, and erythrite, and as hydrated or anhydrous arsenates. Arsenates are similar to phosphates since arsenic (As) and phosphorus (P) occur in group 15 (or VA) of the periodic table. Unlike phosphates, arsenates are not readily lost from minerals due to weathering. They are the predominant form of inorganic arsenic in aqueous aerobic environments. On the other hand, arsenite is more common in anaerobic environments, more mobile, and more toxic than arsenate. Arsenite is 25–60 times more toxic and more mobile than arsenate under most environmental conditions. Arsenate can lead to poisoning, since it can replace inorganic phosphate in the glyceraldehyde-3-phosphate --> 1,3-biphosphoglycerate step of glycolysis, producing 1-arseno-3-phosphoglycerate instead. Although glycolysis continues, 1 ATP molecule is lost. Thus, arsenate is toxic due to its ability to uncouple glycolysis. Arsenate can also inhibit pyruvate conversion into acetyl-CoA, thereby blocking the TCA cycle, resulting in additional loss of ATP.
In enzymology, an aldehyde ferredoxin oxidoreductase (EC 1.2.7.5) is an enzyme that catalyzes the chemical reaction
Molybdenum is an essential element in most organisms. It is most notably present in nitrogenase which is an essential part of nitrogen fixation.
