Human hydroxymethylglutaryl-coenzyme A reductase (HMGCR) and statin sensitivity.

While statins, hydroxymethylglutaryl-coenzyme A reductase (HMGCR) inhibitors, are clinically proven to reduce plasma cholesterol levels, a wide variation in inter-individual response to statin therapy has been observed. Pharmacogenetic studies have identified multiple loci that potentially contribute towards the statin response, including the HMGCR gene. To examine, if a statin-resistant, catalytically-active isoform of the human HMGCR could be generated, we have rationally altered the protein to include additional residues in the flap domain, which has a role in statin binding. Comparative enzyme assays with purified wild-type and mutant isoforms reveal the alteration imposes a slight (38%) decrease in the K(app)(M) for the substrate, a near 2-fold increase in turnover number, and a 480% increase in the Ki for lovastatin. Thus, alterations in HMGCR could contribute towards the synergistic effects of multiple loci in the statin response.