酪氨酸酶对苯肼的氧化作用。

The oxidation of phenylhydrazine by tyrosinase.

机构信息

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

出版信息

Appl Biochem Biotechnol. 2013 Apr;169(8):2420-9. doi: 10.1007/s12010-013-0165-7. Epub 2013 Mar 2.

DOI:10.1007/s12010-013-0165-7

Abstract

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.

摘要

酪氨酸酶被发现能够催化苯肼氧化为苯酚的反应，该反应与通常由酪氨酸酶进行的反应不同。通过测量苯酚形成的初始速度（25°C）来研究该反应的动力学。苯肼氧化的 k cat 和 K M 值分别为 11.0 s(-1)和 0.30 mM。通过硝基四唑蓝（NBT）测定法监测酪氨酸酶氧化苯肼过程中超氧化物的生成。在苯肼-酪氨酸酶反应中，产生 1 摩尔苯酚和 1/6 摩尔超氧化物需要 1 摩尔氧气。超氧化物歧化酶分解超氧化物可提高苯肼氧化的速率常数。苯肼被酪氨酸酶氧化生成的苯酚，在苯肼被酪氨酸酶氧化几乎完成后，进一步被酪氨酸酶氧化为邻醌。