Canadian Medical Guide > Chemicals and Drugs > Enzymes and Coenzymes > Enzymes > Oxidoreductases Terms and Definitions

Oxidoreductases

Medical Definition:	The class of all enzymes catalyzing oxidoreduction reactions. The substrate that is oxidized is regarded as a hydrogen donor. The systematic name is based on donor:acceptor oxidoreductase. The recommended name will be dehydrogenase, wherever this is possible; as an alternative, reductase can be used. Oxidase is only used in cases where O2 is the acceptor. (Enzyme Nomenclature, 1992, p9)
Guide Notes:	X refs OXIDASES; REDUCTASES & DEHYDROGENASES are GEN only: see Tree D8 under OXIDOREDUCTASES for all indentions & choose the most specific
Also Called:	Oxidase
CAS Number:	EC 1.

Oxidoreductases Categories.

	5,10-Methylenetetrahydrofolate Reductase (FADH2) - An FAD-dependent oxidoreductase found primarily in BACTERIA. It is specific for the reduction of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate. This enzyme was formerly listed as EC 1.1.1.68 and 1.1.99.15.
	Alcohol Oxidoreductases - A subclass of enzymes which includes all dehydrogenases acting on primary and secondary alcohols as well as hemiacetals. They are further classified according to the acceptor which can be NAD+ or NADP+ (subclass 1.1.1), cytochrome (1.1.2), oxygen (1.1.3), quinone (1.1.5), or another acceptor (1.1.99).
	Aldehyde Oxidoreductases
	Amine Oxidoreductases - Enzymes catalyzing the dehydrogenation of secondary amines, introducing a C=N double bond as the primary reaction. In some cases this is later hydrolyzed.
	Amino Acid Oxidoreductases - A class of enzymes that catalyze oxidation-reduction reactions of amino acids. EC 1.4.-.
	Ascorbate Oxidase - An enzyme that converts ascorbic acid to dehydroascorbic acid. EC 1.10.3.3.
	Ceruloplasmin
	Hydrogenase - An enzyme found in bacteria. It catalyzes the reduction of ferredoxin and other substances in the presence of molecular hydrogen and is involved in the electron transport of bacterial photosynthesis. EC 1.18.99.1.
	Ketone Oxidoreductases
	Laccase - A copper-containing oxidoreductase enzyme that catalyzes the oxidation of 4-benzenediol to 4-benzosemiquinone. It also has activity towards a variety of O-quinols and P-quinols. It primarily found in FUNGI and is involved in LIGNIN degradation, pigment biosynthesis and detoxification of lignin-derived products.
	Luciferase - Any one of several enzymes that catalyze the bioluminescent reaction in certain marine crustaceans, fish, bacteria, and insects. The enzyme is a flavoprotein; it oxidizes LUCIFERINS to an electronically excited compound that emits energy in the form of light. The color of light emitted varies with the organism. The firefly enzyme is a valuable reagent for measurement of ATP concentration. (Dorland, 27th ed) EC 1.13.12.-.
	Methylenetetrahydrofolate Dehydrogenase (NAD+) - A NAD-dependent oxidoreductase that catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5,10-methenyl-tetrahdyrofolate. It has been found in a variety of microorganisms.
	Methylenetetrahydrofolate Dehydrogenase (NADP) - An NADP-dependent oxidoreductase that catalyses the conversion of 5,10-methyleneterahydrofolate to 5,10-methenyl-tetrahydrofolate. In higher eukaryotes a trifunctional enzyme exists with additional METHENYLTETRAHYDROFOLATE CYCLOHYDROLASE and FORMATE-TETRAHYDROFOLATE LIGASE activity. The enzyme plays an important role in the synthesis of 5-methyltetrahydrofolate, the methyl donor for the VITAMIN B12-dependent remethylation of HOMOCYSTEINE to METHIONINE via METHIONINE SYTHASE.
	Mixed Function Oxygenases - Widely distributed enzymes that carry out oxidation-reduction reactions in which one atom of the oxygen molecule is incorporated into the organic substrate; the other oxygen atom is reduced and combined with hydrogen ions to form water. They are also known as monooxygenases or hydroxylases. These reactions require two substrates as reductants for each of the two oxygen atoms. There are different classes of monooxygenases depending on the type of hydrogen-providing cosubstrate (COENZYMES) required in the mixed-function oxidation.
	NADH, NADPH Oxidoreductases - A group of oxidoreductases that act on NADH or NADPH. In general, enzymes using NADH or NADPH to reduce a substrate are classified according to the reverse reaction, in which NAD+ or NADP+ is formally regarded as an acceptor. This subclass includes only those enzymes in which some other redox carrier is the acceptor. (Enzyme Nomenclature, 1992, p100) EC 1.6.
	Nitrogenase - An enzyme system that catalyzes the fixing of nitrogen in soil bacteria and blue-green algae (CYANOBACTERIA). EC 1.18.6.1.
	Nitroreductases - Enzymes which reduce nitro groups. A variety of compounds can act as acceptors. If NADH or NADPH are the acceptors, the enzymes are classified as EC 1.6.6.- .
	Oxidoreductases Acting on CH-CH Group Donors - A subclass of enzymes which includes all dehydrogenases acting on carbon-carbon bonds. This enzyme group includes all the enzymes that introduce double bonds into substrates by direct dehydrogenation of carbon-carbon single bonds.
	Oxidoreductases, O-Demethylating - Drug metabolizing enzymes which oxidize methyl ethers. Usually found in liver microsomes.
	Oxygenases
	Peroxidases
	Protein Disulfide Reductase (Glutathione) - An enzyme that catalyzes the reduction of a protein-disulfide in the presence of glutathione, forming a protein-dithiol. Insulin is one of its substrates. EC 1.8.4.2.
	Sulfite Oxidases - A molybdohemoprotein which catalyzes the terminal reaction in the oxidative degradation of sulfur-containing amino acids with the formation of a sulfate. Cytochrome c, ferricyanide and molecular oxygen can act as acceptors. A deficiency is manifested by brain damage and mental deterioration. EC 1.8.2.1 utilizes ferricytochrome C as acceptor. EC 1.8.3.1 uses molecular oxygen.
	Sulfite Reductases - Hydrogen sulfide:(acceptor) oxidoreductases. Enzymes which reversibly catalyze the oxidation of hydrogen sulfide in the presence of various acceptors to sulfite and a reduced acceptor. EC 1.8.1.2 utilizes NADP+ as the acceptor. EC 1.8.7.1 utilizes oxidized ferredoxin as acceptor and EC 1.8.99.1 will utilize a variety of acceptors.
	Superoxide Dismutase - An oxidoreductase that catalyzes the reaction between superoxide anions and hydrogen to yield molecular oxygen and hydrogen peroxide. The enzyme protects the cell against dangerous levels of superoxide. EC 1.15.1.1.
	Urate Oxidase - An enzyme that catalyzes the conversion of urate and unidentified products. It is a copper protein. The initial products decompose to form allantoin. EC 1.7.3.3.

Oxidoreductases Medical Definitions and Terms

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