Mammalian protein geranylgeranyltransferase-I: substrate specificity, kinetic mechanism, metal requirements, and affinity labeling.
Mammalian protein geranylgeranyltransferase-I: substrate specificity, kinetic mechanism, metal requirements, and affinity labeling.
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哺乳动物蛋白香叶基香叶基转移酶-I：底物特异性、动力学机制、金属要求和亲和标记。
DOI：
10.1021/bi00004a029
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发表时间：
1995
期刊：
影响因子：
2.9
通讯作者：
Gelb,MH
中科院分区：
文献类型：
--
作者：
Yokoyama,K;McGeady,P;Gelb,MH
1994年10月5日接收的修订版Mandarin pt ®摘要：蛋白质香叶基香叶基转移酶-I（PGGT-I）催化20-碳异戊二烯基从香叶基香叶基焦磷酸转移到各种真核蛋白质C-末端附近的半胱氨酸残基。从牛脑的同质PGGT-I的动力学分析表明，反应遵循顺序pathwayin的异戊二烯供体或受体可以首先绑定到酶和反应操作在稳态，而不是在快速平衡。异戊烯基受体而不是异戊烯基供体对底物的抑制表明，香叶基香叶基焦磷酸首先与游离酶结合是动力学上优选的途径。这是支持的同位素捕获实验表明，三元复合物继续产品的速度比释放的香叶基香叶基焦磷酸从复杂的。香叶基香叶基焦磷酸与PGGT-Ⅰ相互作用的Km值受与酶结合的异戊烯基受体结构的显著影响。PGGT-1的底物特异性的详细分析揭示，含有C-末端亮氨酸的肽（kCM/Ki = 1-5 × 105 M-1 s-1）比以丝氨酸（kCM/Ki = 2-4 × 103 M-1 s-1）或苯丙氨酸（kCM/Ki = 0.5 × 103 M-1 s-1）结束的肽更优选。PGGT-I还催化具有C-末端亮氨酸的肽的法尼基化;法尼基化的kcat和法尼基焦磷酸的Km与香叶基香叶基化的那些相似，但肽的Km高30倍。焦磷酸香叶酯被PGGT-I利用，但是较差的底物。
Revised Manuscript Received October 5, 1994® abstract: Protein geranylgeranyltransferase-I (PGGT-I) catalyzes the transfer of the 20-carbon prenyl group from geranylgeranyl pyrophosphate to the cysteine residue near the C-termini of a variety of eukaryotic proteins. Kinetic analysis of homogenous PGGT-I from bovine brain reveals that the reaction follows a sequential pathwayin which either prenyl donor or acceptor can bind first to the enzyme and that the reaction operates at steady-state rather than at rapid equilibrium. Substrate inhibition by prenyl acceptor but not by prenyl donor suggests that geranylgeranyl pyrophosphate binding first to free enzyme is the kinetically preferred pathway. This is supported by isotope trapping experiments which show that the ternary complex goes on to products faster than the release of geranylgeranyl pyrophosphate from the complex. The Km for the interaction of geranylgeranyl pyrophosphate with PGGT-I is markedly affected by the structure of the prenyl acceptor boundto the enzyme. A detailed analysis of the substrate specificity of PGGT-I reveals that peptides which contain a C-terminal leucine are preferred (kCM/K\i= 1—5 x 105 M-1 s_1) to those that end in serine (kcJK\i= 2—4 x 103* M-1 s_1) or phenylalanine (kcJK\\—0.5 x 103 M-1 s-1). PGGT-I also catalyzes the famesylation of peptides that have a C-terminal leucine; kcat for famesylation and Km for famesyl pyrophosphate are similar to those for geranylgeranylation, but the Km for the peptide is 30-fold higher. Geranyl pyrophosphate is utilized by PGGT-I but is a poor substrate.