N. Nishi, M. Morishige, A. Tsutsumi
Feb 1, 1983
Citations
0
Influential Citations
6
Citations
Journal
International Journal of Biological Macromolecules
Abstract
Abstract Catalytic activities of Boc-Asp-β-Ala-Gly-Ser-β-Ala-Gly-His-β-Ala-Gly-OEt(Boc-9-Oet), Boc-Asp-β-Ala-Gly-Ser-β-Ala-Gly-His-β-Ala-Gly-OH(Boc-9-OH), cyclo(Asp-β-Ala-Gly-Ser-β-Ala-Gly-His-β-Ala-Gly) (Cyclic 9) and poly(Asp-β-Ala-Gly-Ser-β-Ala-Gly-His-β-Ala-Gly) (Poly 9) in the Hydrolysis of p-nitrophenyl acetate were investigated in detail and compared with each other and with poly(His-β-Ala-Gly) (Poly 3) which has no Ser and Asp residues. Generally, Poly 3 was less active than the others, which contain Ser and Asp residues together with the His residue. The reaction rate-substrate concentration for Boc-9-OEt, Boc-9-OH. Cyclic 9 and Poly 3 gave straight lines, while that for Poly 9 showed slightly the tendency of saturation at high substrate concentration. The reaction rates were all proportional to the concentration of the peptides. All peptides gave similar, sigmoid-type pH-kcat profiles. The pK values obtained from these pH-kcat profiles agreed fairly well with those of histidine residues obtained from 13C n.m.r. chemical shifts, which suggests that the predominant participating functional group in the catalytic reaction is the imidazole group in the histidine residue. The pK values of the His residue in peptides with the -Asp-β-Ala-Gly-Ser-β-Ala-Gly-His-β-Ala-Gly- sequence were shifted to higher pH region compared with Poly 3, suggesting that the effect of the carboxyl group in the Asp residue and the extents of pK-shift for linear peptides were larger than for Cyclic 9 or Poly 9. The catalytic reaction rates by Boc-9-OEt or Cyclic 9 increased steadily with increase in temperature, while the reaction rate-temperature profiles for Poly 9 and Poly 3 gave the optimum temperatures at around 40–50°C.