The oxidation of phenylhydrazine by tyrosinase.

Yi-Ming Sung, Srivardhan Reddy Gayam, Shu-Pao Wu

Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan.

Applied biochemistry and biotechnology 2013 Apr

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Tyrosinase was found to catalyze the oxidation of phenylhydrazine to phenol in a reaction that did not resemble those typically performed by tyrosinase. The kinetics of this reaction was investigated by measuring the initial velocity of the formation of phenol (25 °C). The values of k cat and K M for the oxidation of phenylhydrazine were obtained as 11.0 s(-1) and 0.30 mM, respectively. The generation of superoxides during the oxidation of phenylhydrazine by tyrosinase was monitored by nitroblue tetrazolium (NBT) assay. In the phenylhydrazine-tyrosinase reaction, 1 mol O2 was required for the production of 1 mol phenol and 1/6 mol superoxide. The decomposition of superoxide by superoxide dismutase enhanced the rate constant of the oxidation of phenylhydrazine. Phenol formed in the oxidation of phenylhydrazine by tyrosinase was further oxidized by tyrosinase to an o-quinone, after the oxidation of phenylhydrazine by tyrosinase was almost completed.

Citation

Yi-Ming Sung, Srivardhan Reddy Gayam, Shu-Pao Wu. The oxidation of phenylhydrazine by tyrosinase. Applied biochemistry and biotechnology. 2013 Apr;169(8):2420-9