Mechanism of pyridoxal phosphate-dependent enzymatic amino-acid racemization
Abstract
Conversion of L-[α-2H]alanine in H2O and unlabelled L-alanine in 2H2O into D-alanine, under nearly single-turnover conditions, with tyrosine phenol-lyase and with amino-acid racemase from Pseudomonas striata showed significant internal return of the α-hydrogen; the results support a single base mechanism for the racemization reactions catalysed by these two pyridoxal phosphate enzymes but with a third enzyme, alanine racemase from E. coli, the results were inconclusive, showing no detectable α-hydrogen return.