Accelerating Effect of Histidylhistidine on the Copper (II)-Catalyzed Oxidation of Ascorbic Acid

概要

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The effect of histidylhistidine on the copper (II)-catalyzed oxidation of ascorbic acid was investigated kinetically by the polarographic technique. At pH 3.8 histidylhistidine had an accelerating effect on the copper (II)-catalyzed oxidation. In contrast, at pH above 5.0 it exerted an inhibitory effect. The visible and CD spectra of the copper (II)-histidylhistidine system obtained at pH 3.8 and 5.9 indicate that different types of complex species are present predominantly at each pH. That is, at the former pH copper (II) is linked by a coordinate bond to the N-groups of the two imidazole rings in histidylhistidine, while at the latter pH two other N-groups take part in further bond formation. It appears that lability of two of the four coordinate bonds in the copper (II)-histidylhistidine complexes with respect to ligand substitution is a prerequisite for catalytic activity. The effects of histidine, imidazole and acetylhistidine on the copper (II)-catalyzed oxidation of ascorbic acid were compared. The results suggest that the accelerating effect of histidylhistidine arises from the two imidazole rings in the molecule.
公益社団法人日本薬学会の論文
1980-08-25