Coordination chemical studies on metalloenzymes. Measurement of binding constant between apo-tyrosinase and copper ion |
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Authors: | Y Kidani K Ohkuma J Hirose M Noji |
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Affiliation: | Faculty of Pharmaceutical Sciences, Nagoya City University, Tanabe-dori, Mizuho-ku, Nagoya, 467 Japan |
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Abstract: | The behavior of complexing agents for the copper removal reaction was studied by the equilibrium dialysis method. In the copper removal reaction, complexing agents are divided into two types: those that are reducing agents and those that are not. Sodium cyanide and sodium thiosulfate are of the first type, and 8-hydroxyquinoline-5-sulfonic acid, 2,2′-bipyridyl, and picolinic acid are of the second type. From equilibrium dialysis with the first type of complexing agent, the apparent binding constant (pH 6.0) between cuprous ions and apotyrosinase was calculated to be 1015m?1. Similarly, the apparent binding constant (pH 6.0) between cupric ions and apo-tyrosinase was about 1013m?1, which was calculated from equilibrium dialysis with the second type of complexing agent. The apparent binding constant between cuprous ions and apo-tyrosinase was larger than that between cupric ions and apo-tyrosinase. |
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Keywords: | Author to whom all correspondence should be addressed. |
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