Y-Glutamyl phosphate

In subsequent experiments (66), this locked substrate was used to obtain evidence for the hypothesis (67) that enzyme-bound y-glutamyl phosphate 14 is an intermediate in the enzyme-catalyzed reaction. All attempts to isolate this acyl phosphate 14 have failed (66), presumably because of the marked tendency of this intermediate to cyclize to pyrrolidonecarboxyUc acid, 15, and to hydrolyze to glutamic acid. 

The kinetic reaction mechanism appears to be random, and for the reaction to proceed, all substrates must reside as a E-D-Ala-D-Ala-MgATP quaternary complex. Except for its activation of an a-carboxylate to form a peptide bond, the enzyme s mechanism appears to be completely analogous to that catalyzed by glutamine synthetase, which forms a y-glutamyl-phosphate intermediate. There is strong evidence for the participation... 

This enzyme [EC 1.2.1.41], also known as y-glutamyl-phosphate reductase and glutamate-5-semialdehyde dehydrogenase, catalyzes the reaction of L-glutamate 5-semialdehyde with orthophosphate and NADP+ to produce L-y-glutamyl 5-phosphate and NADPH. 

ISOTOPE TRAPPING BOROHYDRIDE REDUCTION y-Glutamyl phosphate reductase,... 

Seddon, A.P. Zhao, K.Y. Meister, A. Activation of glutamate by y-gluta-mate kinase formation of y-cis-cycloglutamyl phosphate, an analog of y-glutamyl phosphate. J. Biol. Chem., 264, 11326-11335 (1989)... 

Meijer, P.-J. Lilius, G, Holmberg, N. Bulow, L. An artificial bifunctional enzyme, y-glutamyl kinase/y-glutamyl phosphate reductase, improves NaCl tolerance when expressed in Escherichia coli. Biotechnol. Lett, 18, 1133-1138 (1996)... 

The y-glutamyl phosphate formed in this step is a mixed anhydride of glutamic acid and phosphoric acid. It is activated toward nucleophilic acyl substitution and gives glutamine when attacked by ammonia. 

Write a stepwise mechanism for the formation of glutamine on y-glutamyl phosphate. 

Midlefort and Rose (95) used an isotope scrambling method to detect the rapid and reversible formation of a y-glutamyl phosphate adduct on the... 

Our studies of the substrates [glutamate (I) and ATP] and of substrate analogs [AMP-P-(CH2)-P and methionine sulfoximine] reveal interactions between both substrate sites and both metal ion sites. Previously mentioned studies by Meister s group showed that the irreversible inhibition of glutamine synthetase in the presence of L-methionine (S)-sulfoximine and ATP was due to formation of the sulfoximine phosphate (IV). The tetrahedral geometry at the sulfur atom of the sulfoximine was suggested to be a mimic of the active structure of the adduct of y-glutamyl phosphate and ammonia (III). Data in our laboratory provide spectroscopic evidence that methionine... 

In the conversion of the /V-acetyl-y-glutamyl phosphate to A-acetylglutamic-y-semialdehyde (fig. 22.2), two processes occur An elimination of a phosphate and a reduction. Which step occurs first Also can you propose a reason for the use of the phosphate group in the first place ... 

First, glutamate (26) and ATP are bound to protein and phosphorylation of glutamate proceeds. Resulting y-glutamyl phosphate (30) is a reactive intermediate, which is able to undergo a nucleophilic substitution by ammonia via tetrahedral transition state and thus glutamine (27) is formed. 

ARG5,6 Protein that is processed in the mitochondrion to yield acetylglutamate kinase and N-acetyl-y-glutamyl-phosphate reductase, which catalyze the second and third steps in arginine biosynthesis enzymes form a complex with Arg2p... 

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