Bem E M, Mailer K, Elson C M
Can J Biochem Cell Biol. 1985 Dec;63(12):1212-6. doi: 10.1139/o85-152.
The effect of phenylmercury and methylmercury on rat liver glutathione peroxidase (GSH X Px) is investigated and compared with that of Hg(II) and with some previously reported results for Cd(II). Analysis of the kinetics of metal binding to the enzyme gives apparent inhibition rate constants: kc = 9.7 mM-1 min-1 for all three mercury compounds and 75 mM-1 min-1 for CdCl2. Glutathione (0.2 mM) protects the enzyme from metal inhibition, decreasing the apparent inhibition rate constants (kc) by 3.6 times for mercury compounds and 4.4 times for CdCl2. KI for the three mercury compounds is found to be 53 microM. It is unexpected that the same value of KI exists for all three forms of mercury studied and that inhibition of the enzyme by the metals is a relatively slow process. For Cd(II) the value of KI is 8.5 microM. It is suggested that inhibition of GSH X Px enzyme activity by cadmium, mercury, and organic mercury salts may not be due to simple complexation of the active site selenium moiety but may be due to a slower process, e.g., an alteration of the enzyme tertiary or quaternary structure.
研究了苯基汞和甲基汞对大鼠肝脏谷胱甘肽过氧化物酶（GSH X Px）的影响，并与汞（II）的影响以及一些先前报道的镉（II）的结果进行了比较。对金属与该酶结合动力学的分析得出表观抑制速率常数：三种汞化合物的kc均为9.7 mM-1 min-1，氯化镉的kc为75 mM-1 min-1。谷胱甘肽（0.2 mM）可保护该酶免受金属抑制，使汞化合物的表观抑制速率常数（kc）降低3.6倍，使氯化镉的表观抑制速率常数降低4.4倍。发现三种汞化合物的KI为53 microM。令人意外的是，所研究的三种汞形式的KI值相同，并且金属对该酶的抑制是一个相对缓慢的过程。对于镉（II），KI值为8.5 microM。有人提出，镉、汞和有机汞盐对GSH X Px酶活性的抑制可能不是由于活性位点硒部分的简单络合，而是可能由于一个较慢的过程，例如酶的三级或四级结构的改变。
