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l-Glutamine d-fructose 6-phosphate amidotransferase from bovine retina

1970; Elsevier BV; Volume: 9; Issue: 1 Linguagem: Inglês

10.1016/s0014-4835(70)80052-5

1096-0007

Roger G. Mazlen, Consuelo G. Muellenberg, Paul J. O’Brien,

Glycosylation and Glycoproteins Research

l -Glutamine d -fructose 6-phosphate amidotransferase (EC 2.6.1.16) which catalyzes the formation of glucosamine 6-phosphate has been isolated from bovine retina as a relatively stable preparation. The Michaelis constant (Km) for glutamine is 0·35 m m and that for fructose 6-phosphate is 0·4 m m . The enzyme exhibits feedback inhibition by uridine diphosphate-N-acetyl- d -glucosamine but not by other related compounds. The Km for fructose 6-phosphate is not affected by variations in the concentrations of either uridine diphosphate-N-acetyl- d -glucosamine or l -glutamine, the latter in the presence or absence of uridine diphosphate-N-acetyl- d -glucosamine. An analog of l -glutamine, 6 diazo-5-oxo- l -norleucine exhibits competitive inhibition with respect to l -glutamine. This analog also partially relieves the inhibition produced by uridinediphosphate-N-acetyl- d -glucosamine at high glutamine concentrations.