The distinction between γ-glutamylhydroxamate synthetase and l-glutamine–hydroxylamine glutamyltransferase activities in rat tissues. Studies in vitro
The distinction between γ-glutamylhydroxamate synthetase and l-glutamine–hydroxylamine glutamyltransferase activities in rat tissues. Studies in vitro
复制标题
大鼠组织中γ-谷氨酰异羟肟酸合成酶和L-谷氨酰胺-羟胺谷氨酰转移酶活性的区别体外研究。
DOI：
10.1042/bj1330049
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发表时间：
1973
影响因子：
4.1
通讯作者：
A. Herzfeld
中科院分区：
文献类型：
--
作者：
A. Herzfeld
测量组织中谷氨酰胺合成潜力的两种常见方法是通过谷氨酸合成（谷氨酰异羟肟酸合成酶反应）或通过谷氨酰胺转移（谷氨酰转移酶反应）形成γ-谷氨酰异羟肟酸的速率;然而，尚未确定任何一种反应都是谷氨酰胺合成酶的特异性测量。通过从几种大鼠组织的水匀浆中差别提取谷氨酰异羟肟酸合成酶和谷氨酰转移酶活性，我获得了一种富含谷氨酰异羟肟酸合成酶活性但几乎没有谷氨酰转移酶活性的提取物，以及一种被颗粒中的脱氧胆酸盐增溶的级分，它几乎不含谷氨酰异羟肟酸合成酶活性，但含有大部分原始谷氨酰转移酶活性。谷氨酰胺的合成在数量上与谷氨酰异羟肟酸合成酶形成的γ-谷氨酰异羟肟酸相似，在水浸提物中被催化，但在颗粒部分中不被催化。由谷氨酰异羟肟酸合成酶和谷氨酰转移酶形成的γ-谷氨酰异羟肟酸显示出不同的底物和金属特异性，并且可以被L-甲硫氨酸亚砜亚胺、磷酸盐和腺嘌呤核苷酸差异性地抑制。谷氨酰胺和γ-谷氨酰异羟肟酸通过谷氨酰异羟肟酸合成酶而不是谷氨酰转移酶形成之间的一致性，以及谷氨酰异羟肟酸合成酶和谷氨酰转移酶活性的不同溶解度，表明这两种活性并非不可分割地相关;因此，它们不能仅由相同的蛋白质催化。
Two common ways of measuring the potential for glutamine synthesis in a tissue are the rates of formation of γ-glutamylhydroxamate either by synthesis from glutamate (the glutamylhydroxamate synthetase reaction) or by transfer from glutamine (the glutamyltransferase reaction); it has not been established, however, that either reaction is a specific measure of glutamine synthetase. By differential extraction of glutamylhydroxamate synthetase and glutamyltransferase activities from water homogenates of several rat tissues I obtained an extract, rich in glutamylhydroxamate synthetase activity but nearly devoid of glutamyltransferase activity, and a fraction, solubilized by deoxycholate from the pellet, which contained virtually no glutamylhydroxamate synthetase activity but most of the original glutamyltransferase activity. Synthesis of glutamine, quantitatively similar to the γ-glutamylhydroxamate formed by glutamylhydroxamate synthetase, is catalysed in the water extract but not in the particulate fraction. γ-Glutamylhydroxamate formation by glutamylhydroxamate synthetase and glutamyltransferase shows discrepant substrate and metal specificities and can be differentially inhibited by l-methionine sulphoximine, phosphate and adenine nucleotides. The concordance between the formation of glutamine and γ-glutamylhydroxamate by glutamylhydroxamate synthetase but not by glutamyltransferase and the different solubilities of the glutamylhydroxamate synthetase and glutamyltransferase enzyme activities demonstrate that these two activities are not inextricably associated; they therefore cannot be catalysed exclusively by the same protein.