Substrate Specificity of Honeydew Melon Protease D, a Plant Serine Endopeptidase

概要

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The substrate specificity of honeydew melon (Cucumis melo var. inodorus Naud) protease D was studied by the use of synthetic substrates and oligopeptides derived from a protein hydrolyzate. The hydrolysis rates of succinyl-(L-Ala)_<1-3>-p-nitroanilide (Suc-(Ala)_<1-3>-pNA) the hydrolysis rate progressively rose in proportion to the increased chain length. Benzyloxycarbonyl-L-tyrosine p-nitrophenyl ester (Z-Tyr-ONp) and benzoyl-L-tyrosine ethyl ester (Bz-Tyr-OEt) were cleaved by honeydew melon protease D, but benzoyl-L-arginine p-nitroanilide (Bz-Arg-pNA), benzyloxycarbonyl-L-lysine p-nitrophenyl ester (Z-Lys-ONp) and tosyl-L-arginine methyl ester (Tos-Arg-OMe) were not hydrolyzed. Contrary to the results obtained by using synthetic substrates, the carboxyl sides of charged amino acid residues were preferentially cleaved by the enzyme in the oligopeptide substrates. The substrates that had charged or polar amino acids at P_2 positions were not cleaved. On the other hand, the non-polar dmino acid or prolitie at P_2 were favored for hydrolysis. The information concerning the subsite of protease D was obtained and is useful for synthesis of a good substrate. As it is distinct from molecular mass, the substrate specificity of honeydew melon protease D is most analogous to cucumisin [EC 3.4.21.25] among serine proteases from cucurbitaceous plants.
社団法人日本農芸化学会の論文
1997-08-23