Hydrolysis of various types of ester substrates with linear,cyclic and polymeric peptides containing His,Ser and Asp residues

Catalytic activities of linear, cyclic and polymeric peptides having the sequences of -Asp-ßAla-Gly-His-ßAla-Gly-(nonapeptide series) and -Asp-eAhx-Ser-eAhx-His-eAhx- (hexapeptide series) in the hydrolysis of various types of ester substrates were compared with one another and with that of poly (-His-ßAla-Gly) (Poly-3) which has no Ser or Asp residues. Hydrolytic activity of the hexapeptide series, the cyclic form in particular, was larger than that of the nonapeptide series in many cases such as in the hydrolysis of N-protected amino acid p-nitrophenyl esters (Z-Gly-ONp, Boc-Ala-ONp, Z- (l and d ) -Leu-ONp, Boc- (l and ) -Phe-ONp) and anionic 3-nitro-4-acetoxybenzoic acid ( NABA ). The activities of the polymeric peptides were generally smaller than those of the linear or cyclic peptides. None of the peptides showed the remarkable activity to the hydrophobic substrate with long chain, p-nitrophenyl laurate ( PNPL ), and they were almost inactive to bulky p-nitrophenyl trimethylacetate ( PNPTMA ) and cationic 3-acetoxy-N-trimethylanilinium iodide ( ANTI ). Enantiomer-selectivity in the hydrolysis of N-protected amino acid p-nitrophenyl esters and solvent isotope effect in the hydrolysis of p-nitrophenyl acetate ( PNPA ) are also reported.