Studies on the catalytic action of poly-.ALPHA.-amino acids. VII. Stereospecificity in the enzyme-like hydrolysis of benzoyl-L(D)-arginine-p-nitroanilides by copoly (Cys, Glu).

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  • NOGUCHI Junzo
    Department of Polymer Science, Faculty of Science, Hokkaido University
  • NISHI Norio
    Department of Polymer Science, Faculty of Science, Hokkaido University
  • TOKURA Seiichi
    Department of Polymer Science, Faculty of Science, Hokkaido University
  • MURAKAMI Umeji
    Department of Polymer Science, Faculty of Science, Hokkaido University

説明

The substrate specificity in the hydrolysis of L-, DL-, and D-BAPA (benzoylarginine-p-nitro-anilide) by copoly (L-Cys, L-Glu) and copoly (D-Cys, D-Glu) was studied, and enzyme-like stereosp-, cific hydrolyses by poly-α-amino acids were identified for the first time. The L-type copolymer hydrolyzed L-BAPA faster than D-BAPA and the rates (v) of BAPA hydrolyses by. L-type copolymer were found to be in the order vL>vDL>vD. On the other hand, the D-type copolymer hydrolysed D-BAPA faster than L-BAPA and the rates of BAPA hydrolyses by D-type copolymer were in the order vD>vDL vL. In all cases, the reaction followed Michaelis-Menten kinetics when the substrate concentration was corrected, and the optimum conditions of the reaction were pH 6.0 and 40°. The activity appeared after a certain amount of BAPA had combined with the polymer. D- and L-substrates combine competitively with the polymer and the different rates of hydrolysis are presumably due to the different substrate configura-tions in relation to the conformation of the active site in the polymer. The polymer shows activity near the range of random coil conformation, where some α-helical conformation is still present. Only some of the cysteine residues in the copolymer are involved in the hydrolytic activity.

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