Interaction of gamma-glutamyl transpeptidase with acivicin.
Interaction of gamma-glutamyl transpeptidase with acivicin.
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发表时间：
1994-08
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通讯作者：
E. Stole;T. Smith;J. Manning;A. Meister
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作者：
E. Stole;T. Smith;J. Manning;A. Meister
acvicin （L-(α S,5S)- α -氨基-3-氯-4,5-二氢-5-异恶唑乙酸）对γ -谷氨酰转肽酶的失活是快速的，被认为是不可逆的，并且与接近1 mol抑制剂/mol酶的结合有关。先前的研究表明[3-14C]acivicin与大鼠肾酶的一个特定羟基（苏氨酸523）结合（被底物阻止）。在目前的工作中，我们发现这种失活可以通过羟胺处理被抑制的酶来逆转。再活化（超过85%完成）与从失活酶中释放出具有3- β -羟基- l - γ -谷氨酰羟酸酯和3-羟基吡咯烷酮-2-羧酸盐性质的化合物有关。我们发现，该酶对acivicin的作用非常缓慢，其速率约为其与谷胱甘肽的正常催化速率的10(-9)，形成三- β -羟基- l -谷氨酸和羟胺。研究结果表明，acivicin的抑制作用涉及到它在酶上转化为一种抑制物质，这种抑制物质显然是通过酯链连接到酶的一个特定羟基上。这种中间体的释放速度非常慢，似乎说明了观察到的抑制作用。
Inactivation of gamma-glutamyl transpeptidase by acivicin (L-(alpha S,5S)-alpha-amino-3-chloro-4,5-dihydro-5-isoxazole acetic acid) is rapid, thought to be irreversible, and associated with binding of close to 1 mol of inhibitor/mol of enzyme. Previous studies with [3-14C]acivicin indicated binding (prevented by substrate) to a specific hydroxyl group (threonine 523) of the rat kidney enzyme. In the present work, we found that such inactivation can be reversed by treating the inhibited enzyme with hydroxylamine. Reactivation (more than 85% complete) is associated with release from the inactivated enzyme of compounds that exhibit the properties of threo-beta-hydroxy-L-gamma-glutamyl hydroxamate and 3-hydroxypyrrolidone-2-carboxylate. We found that the enzyme acts very slowly on acivicin, at a rate that is about 10(-9) that of its normal catalytic rate with glutathione, to form threo-beta-hydroxy-L-glutamate and hydroxylamine. The findings indicate that inhibition by acivicin involves its transformation on the enzyme to an inhibitory species which is attached, apparently by ester linkage, to a specific hydroxyl group of the enzyme. The very slow rate of release of this intermediate appears to account for the observed inhibition.