In enzymology, a 3alpha-hydroxysteroid dehydrogenase (B-specific) () is an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...

that

catalyzes Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycl ...

the

chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and break ...

:androsterone + NAD(P)⁺

\rightleftharpoons

5alpha-androstane-3,17-dione + NAD(P)H + H⁺ The 3 substrates of this enzyme are

androsterone Androsterone, or 3α-hydroxy-5α-androstan-17-one, is an endogenous steroid hormone, neurosteroid, and putative pheromone. It is a weak androgen with a potency that is approximately 1/7 that of testosterone. Androsterone is a metabolite o ...

, NAD⁺, and NADP⁺, whereas its 4 products are 5alpha-androstane-3,17-dione,

NADH Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an aden ...

NADPH Nicotinamide adenine dinucleotide phosphate, abbreviated NADP or, in older notation, TPN (triphosphopyridine nucleotide), is a cofactor used in anabolic reactions, such as the Calvin cycle and lipid and nucleic acid syntheses, which require NADP ...

, and H⁺. This enzyme belongs to the family of

oxidoreductase In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule, the reductant, also called the electron donor, to another, the oxidant, also called the electron acceptor. This group of enzymes usually ...

s, specifically those acting on the CH-OH group of donor with NAD⁺ or NADP⁺ as acceptor, more specifically it is part of the group of

hydroxysteroid dehydrogenase Hydroxysteroid dehydrogenases (HSDs) are a group of alcohol oxidoreductases that catalyze the dehydrogenation of hydroxysteroid A hydroxysteroid is a molecule derived from a steroid with a hydrogen replaced with a hydroxy group. When the hy ...

s. The

systematic name A systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance, out of a specific population or collection. Systematic names are usually part of a nomenclature. A semisystematic name or semitrivial ...

of this enzyme class is 3alpha-hydroxysteroid:NAD(P)⁺ oxidoreductase (B-specific). Other names in common use include hydroxyprostaglandin dehydrogenase, 3alpha-hydroxysteroid oxidoreductase, and sterognost 3alpha. This enzyme participates in 3

metabolic pathways In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell. The reactants, products, and intermediates of an enzymatic reaction are known as metabolites, which are modified by a sequence of chemical rea ...

bile acid biosynthesis Bile acids are steroid acids found predominantly in the bile of mammals and other vertebrates. Diverse bile acids are synthesized in the liver. Bile acids are conjugated with taurine or glycine residues to give anions called bile salts. Primary ...

c21-steroid hormone metabolism C, or c, is the third letter in the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''cee'' (pronounced ), plural ''cees''. History "C" ...

, and

androgen and estrogen metabolism An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This inc ...

Structural studies

As of late 2007, 7 structures have been solved for this class of enzymes, with PDB accession codes , , , , , , and .

References

* * * * EC 1.1.1 NADPH-dependent enzymes NADH-dependent enzymes Enzymes of known structure {{1.1.1-enzyme-stub