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

, a progesterone 5alpha-reductase () is an enzyme 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 recyc ...

the chemical reaction :5alpha-pregnan-3,20-dione + NADP⁺

\rightleftharpoons

progesterone + NADPH + H⁺ Thus, the two substrates of this enzyme are 5alpha-pregnan-3,20-dione and NADP⁺, whereas its 3 products are

progesterone Progesterone (P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the m ...

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 NAD ...

, and H⁺. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-CH group of donor with NAD+ or NADP+ as acceptor. It is a C21-steroid hormone that is a 5α-pregnane substituted with a oxo groups at positions 3 and 20. It is an intermediate in the conversion of progesterone to allopregnalone and isopregnanolone, other common forms of neurosteroids. The systematic name of this enzyme class is 5alpha-pregnan-3,20-dione:NADP+ 5-oxidoreductase. Other names in common use include steroid 5-alpha-reductase, and Delta4-steroid 5alpha-reductase (progesterone).

References

* * EC 1.3.1 NADPH-dependent enzymes Enzymes of unknown structure {{1.3-enzyme-stub