Synthesis and use of isotope-labelled substrates for a mechanistic study on human alpha-methylacyl-CoA racemase 1A (AMACR; P504S)

alpha-Methylacyl-CoA racemase (AMACR) is an important enzyme for the metabolism of branched-chain lipids and drugs. The enzyme is over-expressed in prostate and other cancers. AMACR 1A, the major splice variant, was purified from recombinant E. coli cells as a His-tag protein. Purified enzyme catalysed chiral inversion of both S- and R-2-methyldecanoyl-CoA, with an equilibrium constant of 1.09 +/- 0.14 (2S/2R). Reactions with H-2-labelled substrate showed that loss of the alpha-proton was a prerequisite for chiral inversion. Reactions conducted in (H2O)-H-2 indicated that reprotonation was not stereospecific. These results are the first mechanistic study on any recombinant mammalian alpha-methylacyl-CoA racemase.