The HMG-CoA reductases catalyse the conversion of HMG-CoA to mevalonate, which is the rate-limiting step in the synthesis of isoprenoids like cholesterol. Probably because of the critical role of this enzyme in cholesterol homeostasis, mammalian HMG-CoA reductase is heavily regulated at the transcriptional, translational, and post-translational levels [2].

1: Crystal structure of Pseudomonas mevalonii HMG-CoA reductase at 3.0 angstrom resolution. Lawrence CM, Rodwell VW, Stauffacher CV; Science 1995;268:1758-1762. PMID:7792601

2: The 3-hydroxy-3-methylglutaryl coenzyme-A (HMG-CoA) reductases. Friesen JA, Rodwell VW; Genome Biol 2004;5:248. PMID:15535874