Guat Ling Lee

α-Methylacyl-CoA racemase (AMACR): Metabolic enzyme, drug metabolizer and cancer marker P504S

α-Methylacyl-CoA racemase (AMACR; P504S) catalyzes a key chiral inversion step in the metabolism of branched-chain fatty acids, ibuprofen and related drugs. Protein levels are increased in all prostate and some other cancer cells and it is used as a marker (P504S). The enzyme requires no cofactors and catalyzes its reaction by a stepwise 1,1-proton transfer via an enolate intermediate. The biological role of AMACR in cancer is complex, linking lipid metabolism with nuclear receptor (e.g. FXR and PPAR) activity and expression of enzymes such as cyclooxygenase-2 (COX-2). The roles of the various splice variants and the effects of single-nucleotide polymorphisms (SNPs) in cancers are discussed. A number of rationally designed AMACR inhibitors have been reported in the literature as potential cancer treatments. The opportunities and challenges for development of acyl-CoA esters as inhibitors are discussed from a medicinal chemical viewpoint. Other challenges for drug development include the problems in assaying enzymatic activity and the prediction of structure-activity relationships (SAR). Inhibitors of AMACR have potential to provide a novel treatment for castrate-resistant prostate cancers but this potential can only be realized once the biology is well understood. Recent work on the role of AMACR in parasitic diseases is also reviewed.

High-Throughput Screening to identify novel inhibitors of human α-methylacyl-CoA racemase 1A (AMACR; P504S)

α-Methylacyl-CoA racemase (AMACR; P504S) catalyzes a key step in the degradation of branched-chain fatty acids and is important for the pharmacological activation of Ibuprofen and related drugs. Both the concentration and activity of AMACR are increased in prostate and other cancer cells, and the enzyme is a recognized drug target. However, all of the reported inhibitors are acyl-CoA esters (which do not comply with Lipinski guidelines) or non-specific protein modifying agents. Libraries of ~20,000 drug-like compounds were screened using a novel colorimetric assay; Incubation of R,S-2-3-(2,4-dinitrophenoxy)-2-methylpropanoyl-CoA with active AMACR resulted in the elimination of the strongly yellow 2,4-dinitrophenoxide and allows continuous measurement of activity in a microtitre plate format. Inhibitors were identified by a reduction in the rate of reaction in the presence of the library compound vs. the control. A number of novel reversible inhibitors were identified and their potency determined using dose-response curves. The results demonstrate the utility of the assay for the discovery and characterization of AMACR inhibitors as anti-cancer agents. This work was funded by Prostate Cancer UK (PG14-009), a Biochemical Society Summer Vacation Studentship Award, The Nuffield Foundation and MRC technology.