The mitochondrial glycine cleavage system. Purification and properties of glycine decarboxylase from chicken liver mitochondria.
The mitochondrial glycine cleavage system. Purification and properties of glycine decarboxylase from chicken liver mitochondria.
复制标题
线粒体甘氨酸裂解系统。
DOI：
10.1016/s0021-9258(19)70183-5
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发表时间：
1980
期刊：
影响因子：
--
通讯作者：
G. Kikuchi
中科院分区：
文献类型：
--
作者：
K. Hiraga;G. Kikuchi
甘氨酸脱羧酶，暂称为P-蛋白，被认为是甘氨酸裂解系统的组成部分，从鸡肝线粒体中纯化至表观均一性。P蛋白是一种同源二聚体，其Mr =约200，000，由Mr =约100，000的相同亚基组成。每个亚基似乎含有等摩尔的吡哆醛5 '-磷酸，其可能通过质子化的醛亚胺键与蛋白质结合。P蛋白的等电点为7.2。P-蛋白可以结合甘氨酸，显示其Kd为33 mM，并且可以催化甘氨酸脱羧，即使由P-蛋白单独催化的脱羧速率极低。甘氨酸脱羧的产物为甲胺，甘氨酸的Km为。甲胺可与P蛋白结合，Kd值为63 mM，并抑制甘氨酸脱羧。单独的P-蛋白也可以轻微地催化甘氨酸的羧基碳与CO2的交换，并且交换似乎服从乒乓机制。甘氨酸脱羧和甘氨酸-CO2交换由P-蛋白催化的刺激100倍或更多的添加的硫辛酸，这是一个功能团的H-蛋白。我们可以将P-蛋白定义为甘氨酸脱羧酶，尽管P-蛋白单独仅表现出非常低的催化活性。
Glycine decarboxylase, tentatively called P-protein and considered a constituent of the glycine cleavage system, was purified to apparent homogeneity from chicken liver mitochondria. P-protein is a homodimer having a Mr = approximately 200,000 and consisting of identical subunits with Mr = approximately 100,000. Each subunit appears to contain an equimolar pyridoxal 5'-phosphate which is bound to the protein, possibly through a protonated aldimine linkage. The isoelectric point of P-protein was 7.2. P-protein could bind glycine, showing a Kd of 33 mM for it, and could catalyze glycine decarboxylation even though the rate of decarboxylation catalyzed by P-protein alone was extremely low. The product of glycine decarboxylation was methylamine and the Km for glycine. Methylamine could bind to P-protein, giving a Kd value of 63 mM, and it inhibited the glycine decarboxylation. P-protein alone could also slightly catalyze the exchange of carboxyl carbon of glycine with CO2 and the exchange appeared to obey a ping-pong mechanism. Both glycine decarboxylation and the glycine-CO2 exchange catalyzed by P-protein were stimulated 100-fold or more by the addition of lipoic acid, which is a functional group of H-protein. We may define P-protein as glycine decarboxylase although P-protein alone exhibits only very low catalytic activities.