Using capillary electrophoresis in the optimization of a carboxypeptidase Y catalyzed transpeptidation reaction

A peptide amide, R-Arg-NH2, was produced by carboxypeptidase Y (CPDY)-catalyzed transpeptidation of a peptide, R-Ala-OH in presence of a large excess of Arg-NH2. Baseline separation of R-Ala-OH and R-Arg-NH2 was achieved by free solution capillary electrophoresis (CE) analysis. With CE the reactions could be closely followed with an analysis frequency of 3-6 h-1. Due to a low consumption of sample per CE analysis (1-5 nL introduced, 5-6 microL in the sample vial), the reactions were performed in 100 and 250 microL volumes. Consequently, the optimization experiments consumed limited amounts of enzyme and substrate only. At optimized experimental conditions approximately 90% conversion of the starting peptide, R-Ala-OH, to R-Arg-NH2 was achieved.