Endopeptidases of <i style="">Bacillus subtilis</i> IBTC-3 and <i style="">B. alcalophilus</i> PB92 in synthesis of precursors of biologically active peptides

Abstract

Two endopeptidases (from <i style="">Bacillus subtilis</i> IBTC-3 and from <i style="">B. alcalophilus</i> 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.