EVIDENCE FOR A PROTEIN-KINASE CASCADE IN HIGHER-PLANTS - 3-HYDROXY-3-METHYLGLUTARYL-COA REDUCTASE KINASE
EVIDENCE FOR A PROTEIN-KINASE CASCADE IN HIGHER-PLANTS - 3-HYDROXY-3-METHYLGLUTARYL-COA REDUCTASE KINASE
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DOI：
10.1111/j.1432-1033.1992.tb17364.x
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发表时间：
1992-11-01
期刊：
影响因子：
--
通讯作者：
HARDIE, DG
中科院分区：
文献类型：
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作者：
MACKINTOSH, RW;DAVIES, SP;HARDIE, DG
蛋白质磷酸化是高等植物中公认的一种调节机制，但只有少数几种植物酶被认为是以这种方式调节的，而且相对较少的植物蛋白激酶被表征。AMP激活的蛋白激酶调节哺乳动物脂肪酸、类固醇和类异戊二烯代谢的关键酶，包括3-羟基-3-甲基戊二酰辅酶A(HMG-CoA)还原酶。我们现在证明，在高等植物中有一种活性，根据功能标准，它是AMP激活的蛋白激酶的同系物，尽管它不受AMP调节。植物激酶失活哺乳动物的HMG-CoA还原酶和乙酰辅酶A羧基酶，肽图谱表明，它与哺乳动物的激酶一样，使这些蛋白质上的相同位置磷酸化。然而，对于从植物来源纯化的靶酶，它可以失活HMG-CoA还原酶，但不能失活乙酰-CoA羧基酶。该激酶位于叶细胞的可溶性部分，而不是叶绿体部分，这与它调节HMG-CoA还原酶，从而调节体内异戊二烯生物合成的想法是一致的。植物激酶似乎也是进化过程中高度保守的蛋白激酶级联的一部分，因为该激酶分别被哺乳动物蛋白磷酸酶(2A或2C)和哺乳动物激酶失活和重新激活。这与许多其他哺乳动物蛋白激酶参与信号转导的情况形成了鲜明对比，这些蛋白激酶在高等植物中似乎没有密切的同源物。据我们所知，这是第一个在高等植物中存在蛋白激酶级联的直接证据。
Protein phosphorylation is well established as a regulatory mechanism in higher plants, but only a handful of plant enzymes are known to be regulated in this manner, and relatively few plant protein kinases have been characterized. AMP-activated protein kinase regulates key enzymes of mammalian fatty acid, sterol and isoprenoid metabolism, including 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase. We now show that there is an activity in higher plants which, by functional criteria, is a homologue of the AMP-activated protein kinase, although it is not regulated by AMP. The plant kinase inactivates mammalian HMG-CoA reductase and acetyl-CoA carboxylase, and peptide mapping suggests that it phosphorylates the same sites on these proteins as the mammalian kinase. However, with the target enzymes purified from plant sources, it inactivates HMG-CoA reductase but not acetyl-CoA carboxylase. The kinase is located in the soluble, and not the chloroplast, fraction of leaf cells, consistent with the idea that it regulates HMG-CoA reductase, and hence isoprenoid biosynthesis, in vivo. The plant kinase also appears to be part of a protein kinase cascade which has been highly conserved during evolution, since the kinase is inactivated and reactivated by mammalian protein phosphatases (2A or 2C) and mammalian kinase kinase, respectively. This contrasts with the situation for many other mammalian protein kinases involved in signal transduction, which appear to have no close homologue in higher plants. To our knowledge, this represents the first direct evidence for a protein kinase cascade in higher plants.