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 27-hydroxycholesterol 7alpha-monooxygenase () is an

enzyme 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 ...

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 A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...

:27-hydroxycholesterol + NADPH + H⁺ + O₂

\rightleftharpoons

7alpha,27-dihydroxycholesterol + NADP⁺ + H₂O The 4 substrates of this enzyme are 27-hydroxycholesterol,

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 ...

, H⁺, and O₂, whereas its 3 products are 7alpha,27-dihydroxycholesterol, NADP⁺, and H₂O. 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 paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2 with NADH or NADPH as one donor, and incorporation of one atom o oxygen into the other donor. The systematic name of this enzyme class is 27-hydroxycholesterol,NADPH:oxygen oxidoreductase (7alpha-hydroxylating). This enzyme is also called 27-hydroxycholesterol 7alpha-hydroxylase. It employs one cofactor, heme-thiolate(P-450).

References

* EC 1.14.13 NADPH-dependent enzymes Heme enzymes Enzymes of unknown structure {{1.14.13-enzyme-stub