In enzymology, a hydroxymethylglutaryl-CoA reductase (NADPH) () is an enzyme that catalyzes the chemical reaction
The three substrates of this enzyme are (R)-mevalonate, coenzyme A (CoA), and oxidised nicotinamide adenine dinucleotide phosphate (NADP<sup>+</sup>). Its products are (S)-3-hydroxy-3-methylglutaryl-CoA, reduced NADPH, and two protons.
This enzyme belongs to the family of oxidoreductases, to be specific those acting on the CH-OH group of donor with NAD<sup>+</sup> or NADP<sup>+</sup> as acceptor. This enzyme participates in biosynthesis of steroids including cholesterol. The statin class of anticholesterol drugs act through inhibiting this enzyme.
The systematic name of this enzyme class is (R)-mevalonate:NADP<sup>+</sup> oxidoreductase (CoA-acylating). Other names in common use include:
As of late 2007, 12 structures have been solved for this class of enzymes, with PDB accession codes , , , , , , , , , , , and .