enzymology An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

, a 3alpha(or 20beta)-hydroxysteroid dehydrogenase () is an

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

that

catalyzes Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

the

chemical reaction A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, ...

: androstan-3alpha,17beta-diol + NAD⁺

\rightleftharpoons

17beta-hydroxyandrostan-3-one + NADH + H⁺ Thus, the two substrates of this enzyme are androstan-3alpha,17beta-diol and NAD⁺, whereas its 3

products Product may refer to: Business * Product (business), an item that can be offered to a market to satisfy the desire or need of a customer. * Product (project management), a deliverable or set of deliverables that contribute to a business solution ...

are 17beta-hydroxyandrostan-3-one,

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 ade ...

, 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 ut ...

s, specifically those acting on the CH-OH group of donor with NAD⁺ or NADP⁺ as acceptor. 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 semitrivi ...

of this enzyme class is 3alpha(or 20beta)-hydroxysteroid:NAD⁺ oxidoreductase. Other names in common use include cortisone reductase, (R)-20-hydroxysteroid dehydrogenase, dehydrogenase, 20beta-hydroxy steroid, Delta4-3-ketosteroid hydrogenase, 20beta-hydroxysteroid dehydrogenase, 3alpha,20beta-hydroxysteroid:NAD⁺-oxidoreductase, NADH-20beta-hydroxysteroid dehydrogenase, and 20beta-HSD. This enzyme participates in

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 in peroxisomes. Bile acids are conjugated with taurine or glycine residues to give anions called bile ...

and c21-steroid hormone metabolism.

Structural studies

As of late 2007, 6

structures A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...

have been solved for this class of enzymes, with PDB accession codes , , , , , and .

References

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