Regulation of Acetyl-Coenzyme A Carboxylase and Acetyl-Coenzyme A Synthetase in Spinach Chloroplasts
Regulation of Acetyl-Coenzyme A Carboxylase and Acetyl-Coenzyme A Synthetase in Spinach Chloroplasts
复制标题
菠菜叶绿体中乙酰辅酶 A 羧化酶和乙酰辅酶 A 合成酶的调控
DOI：
10.1515/znc-1984-3-412
复制
发表时间：
1984
期刊：
影响因子：
--
通讯作者：
K. Heise
中科院分区：
文献类型：
--
作者：
A. Sauer;K. Heise
与从醋酸盐合成叶绿体脂肪酸类似，醋酸盐固定的关键酶、乙酰辅酶A合成酶和乙酰辅酶A羧化酶，在快速Triton X-100裂解的菠菜叶绿体中表现出光激活和黑暗失活。深色叶绿体中二硫苏糖醇对乙酰辅酶A羧化酶的刺激表明该酶的光激活涉及还原当量。但这些酶似乎不仅仅受到激活状态本身的改变的影响，而且由于叶绿体基质的质子、Mg2+-和腺嘌呤核苷酸水平的差异而受到其催化活性变化的影响。因此，从 Triton X-100 裂解的叶绿体中立即提取的两种酶的 pH 依赖性，类似于最近发现的在乙酰辅酶 A 羧化酶的最佳 pH 值约为 8.5 的情况下，乙酸酯脂质掺入完整菠菜叶绿体中的情况。此外，在相同的提取物中，两种酶活性都显示出对 MgATP 和游离 Mg 的假定需求，并且相对于 MgATP 被游离 ATP 和 ADP 竞争性抑制。但由于事实上，与羧化酶活性相反，可提取的乙酰辅酶A合成酶的活性远远超过了破坏前光照叶绿体对乙酸酯的脂质掺入率，乙酰辅酶A合成酶将被排除在从乙酸酯合成脂肪酸的速率限制步骤之外。从乙酸固定的关键酶来看，只有羧化酶似乎参与了乙酸掺入长链脂肪酸的光调节
In analogy to chloroplast fatty acid synthesis from acetate the key enzymes of acetate fixation, acetyl-CoA synthetase and acetyl-CoA carboxylase, in rapidly Triton X-100 lysed spinach chloroplasts show an activation by light and deactivation in the dark. The stim ulation of acetyl-CoA carboxylase by dithiothreitol in darkened chloroplasts points to an involvement of reducing equivalents in the light activation of this enzyme. But more than by alterations of the activation state per se, these enzymes appear to be effected by changes in their catalytic activity due to differences in the proton-, Mg2+- and adenine nucleotide levels of the chloroplast stroma. Thus the pH dependence of both enzymes, as immediately extracted from Triton X-100 lysed chloroplasts, resembles that recently found for lipid incorporation of acetate into intact spinach chloroplasts in the light with an identical pH optim um of about pH 8.5 for the acetyl-CoA carboxylase. Moreover, in the same extracts both enzyme activities show the already postulated requirement for MgATP and free Mg and are com petitively inhibited by free ATP and ADP with respect to MgATP. But on account of the fact, that the extractable acetyl-CoA synthetase as opposed to the carboxylase activities exceed by far the lipid incorporation rates of acetate by illuminated chloroplasts before disruption, acetyl-CoA synthetase will be excluded as rate limiting step in fatty acid synthesis from acetate. From key enzymes of acetate fixation only the carboxylase appears to be involved therefore in the light regulation of acetate incorporation into long-chain fatty acids