ABSTRACT
Two endopeptidases (from Bacillus subtilis IBTC-3 and from B. alcalophilus PB92-commercial preparation) efficiently synthesized amino acid esters (NAc-Tyr-OEt and NAc-Phe-OEt) and dipeptides (NAc-Tyr-Gly-NH2 and NAc-Tyr-Arg-NH2) in organic solvent/water systems. The rate of NAc-Tyr-OEt synthesis mediated by the native subtilisin IBTC-3 was maximum (0.23 Umg-1) in ethanol/5-7% w/v water system, while the highest activity of the freeze-dried enzyme (0.18 Umg-1) was achieved, when water content was 9-10% w/v. The preferred system for dipeptide synthesis (using NAc-Tyr-OEt as acyl donor) by both the enzymes was acetonitrile/4% w/v water. In this system, the maximum yield of NAc-Tyr-GlyNH2 was 71 and 80% and that of NAc-Tyr-Arg-NH2 was 53 and 40% for subtilisin IBTC-3 and peptidase PB92, respectively. In contrast to the peptidase PB92, the subtilisin efficiently catalyzed esterification of NAc-Tyr with 1-butanol and isopropanol.