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Gerry R. Boss Soha D. Idriss Randall C. Willis J. E. Seegmiller 《Analytical biochemistry》1983,130(2)
Glutamine phosphoribosylpyrophosphate amidotransferase (EC 2.4.2.14) catalyzes the transfer of the amide group of glutamine to 5-phospho-α-
-ribose-1-pyrophosphate. It is the first enzyme committed to the synthesis of purines by the de novo pathway. Previous assays of enzyme activity have either measured the phosphoribosylpyrophosphate-dependent disappearance of radioactive glutamine or have linked this reaction to subsequent steps in the purine pathway. A new assay for activity of the enzyme by directly measuring the synthesis of the product of the reaction, 5-β-phosphoribosyl-1-amine, using [1-14C]phosphoribosylpyrophosphate as substrate is described. Substrate and product are separated by thin-layer chromatography and identified by autoradiography. Glutamine or ammonia may be used as substrates; the apparent Km values of the human lymphoblast enzyme are 0.46 m
for glutamine and 0.71 m
for ammonia. GMP is a considerably more potent inhibitor of the human lymphoblast enzyme than is AMP; 6-diazo-5-oxo-
-norleucine inhibits only glutamine-dependent activity and has no effect on ammonia-dependent activity. 相似文献
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