The distribution between gamma-glutamylhydrozamate synthetase and L-glutamine-hydroxylamine glutamyltransferase activities in rat tissues. Studies in vitro.
Two common ways of measuring the potential for glutamine synthesis in a tissue are the rates of formation of gamma-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 gamma-glutamylhydroxamate formed by glutamylhydroxamate synthetase, is catalysed in the water extract but not in the particulate fraction. gamma-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 gamma-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.
D000217:Acyltransferases / Q000378:metabolism*; D000255:Adenosine Triphosphate; D000818:Animals; D001921:Brain / Q000201:enzymology; D002247:Carbon Isotopes; D002848:Chromatography, DEAE-Cellulose; D002855:Chromatography, Thin Layer; D003840:Deoxycholic Acid; D005974:Glutamate-Ammonia Ligase / Q000302:isolation & purification / Q000378:metabolism*; D006877:Hydroxamic Acids; D006898:Hydroxylamines; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008168:Lung / Q000201:enzymology; D008297:Male; D008717:Methionine Sulfoximine; D009132:Muscles / Q000201:enzymology*; D009928:Organ Specificity; D051381:Rats; D011919:Rats, Inbred Strains; D013053:Spectrophotometry; D013347:Subcellular Fractions / Q000201:enzymology; D005723:gamma-Glutamyltransferase / Q000302:isolation & purification / Q000378:metabolism
D002247:Carbon Isotopes; D006877:Hydroxamic Acids; D006898:Hydroxylamines; D003840:Deoxycholic Acid; D008717:Methionine Sulfoximine; D000255:Adenosine Triphosphate; D000217:Acyltransferases; D005723:gamma-Glutamyltransferase; D005974:Glutamate-Ammonia Ligase