甲巯咪唑对蘑菇酪氨酸酶活性的影响。
Effect of methimazole on the activity of mushroom tyrosinase.
作者信息
Andrawis A, Kahn V
出版信息
Biochem J. 1986 Apr 1;235(1):91-6. doi: 10.1042/bj2350091.
Methimazole (1-methyl-2-mercaptoimidazole) inhibits both the mono- and the o-dihydroxyphenolase activities of mushroom tyrosinase when assayed spectrophotometrically. With DL-3,4-dihydroxyphenylalanine as substrate, the inhibition was found to be a mixed-type one with Ki 4.6 X 10(-6) M. We found that methimazole can interact with the oxidation products of o-dihydroxyphenols, probably with o-quinones, to form a conjugate. The conjugate formed between methimazole and o-benzoquinone was separated by chromatography on Sephadex G-10 and was characterized by an absorption maximum at 248-260 nm. Our data suggest that methimazole inhibits mushroom tyrosinase activity in two ways: by conjugating with o-quinones, thereby causing an apparent inhibition in pigmented product formation as judged by the spectrophotometric assay; and by chelating copper at the active site of the enzyme, as judged by assaying the release of 3HHO from L-[3,5-3H]tyrosine.
甲巯咪唑（1-甲基-2-巯基咪唑）在采用分光光度法测定时，可抑制蘑菇酪氨酸酶的单酚酶和邻二酚酶活性。以DL-3,4-二羟基苯丙氨酸作为底物时，发现该抑制作用为混合型，抑制常数（Ki）为4.6×10⁻⁶ M。我们发现甲巯咪唑可与邻二酚的氧化产物相互作用，可能是与邻醌相互作用，形成一种共轭物。甲巯咪唑与邻苯醌形成的共轭物通过葡聚糖凝胶G-10柱色谱法分离，并通过在248 - 260 nm处有最大吸收峰进行表征。我们的数据表明，甲巯咪唑通过两种方式抑制蘑菇酪氨酸酶活性：通过与邻醌共轭，从而在分光光度法测定中导致色素产物形成出现明显抑制；通过螯合酶活性位点的铜，这是通过测定L-[3,5-³H]酪氨酸中³HHO的释放来判断的。
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