Glutamine aminotransferase

See specific amidotransferase GLUTAMINE AMINOTRANSFERASE GlutamineiPRPP amidotransferase, AMIDOPHOSPHORIBOSYLTRANSFERASE GLUTAMINE SYNTHETASE ARSENOLYSIS... 

Glutamine then reacts with a-oxoglutarate to form 2 molecules of glutamic add. This reaction is catalysed by glutamate oxoglutamate aminotransferase (GOGAT) and can be written as ... 

The enzymes glutamate dehydrogenase, glutamine synthetase, and aminotransferases occupy central positions in amino acid biosynthesis. The combined effect of... 

Figure 9.4 Reactions of glutaminolysis the pathway for glutamine oxidation. Reaction 1 is catalysed by glutaminase, reaction 2 by glutamate aminotransferase, and reaction 8 by aspartate aminotransferase all other enzymes are those of the Krebs cycle (3-7). (See also Chapter 8).

Formation of the Initial Cyclitol. The first steps of FOR production are the same as in the biosynthesis of STR in short, the first step in FOR biosynthesis is postulated to be the formation of a myo-inositol monophosphate (D-myo-inositol-3-phosphate or L-myo-inositol-1-phosphate) via the cellular l-myo-inositol-1-phosphate synthase as in the STR pathway (Ca pathway see Section 2.2.1.2). As in the itr-Att-clusters, no gene for this enzyme has been found in the/or-cluster. As a second step in FOR biosynthesis the dephosphorylation of D-myo-inositol-3-phosphate via an inositolmonophosphate phosphatase has to follow. A putative gene product with this activity is that of the ForA protein (cf. Tables 2.17 and 2.18). The cyclitol is postulated to be first converted via two enzymes, a cluster-encoded myo-inositol 3-dehydrogenase (ForG member of the GFO/IDH/MocA oxidoreductase family) and the L-glutamine icy//o-3-inosose 3-aminotransferase (ketocyclitol aminotransferase I ForS), to icy//o-inosamine (3-deoxy-3-amino- cy/to-mositol). 

This enzyme [EC 2.6.1.16], also referred to as glutamine-fructose-6-phosphate aminotransferase (isomerizing), catalyzes the reaction of L-glutamine and o-fructose 6-phosphate to yield L-glutamate and o-glucosamine 6-phosphate. 

See specific aminotransferase Glutamate as a substrate or product, GLUTAMATE DECARBOXYLASE GLUTAMATE DEHYDROGENASE GLUTAMATE SYNTHASE GLUTAMINE SYNTHETASE y-GLUTAMYL TRANSPEPTIDASE LEUCINE AMINOTRANSEERASE LYSINE 6-AMINOTRANSEERASE... 

Terms in bold are defined in aminotransferases 660 transaminases 660 transamination 660 pyridoxal phosphate (PLP) 660 oxidative deamination 661 l-glutamate dehydrogenase 661 glutamine synthetase 662 glutaminase 663 creatine kinase 664... 

Step c of Eq. 24-34 may occur by ring opening to an enol phosphate which ketonizes to the observed product, but step e is a more complex multistep oxidative process.314a,b The last step is transamination to methionine with a glutamine-specific aminotransferase. Another enzyme from Klebsiella converts the same intermediate anion to methylthiopropionate, formate, and CO (Eq. 24-34, step/).315... 

GS in plants is the key enzyme of the GS/GOGAT (glutamine synthetase/g1utamine 2-oxyg1utarate aminotransferase) pathway and thus plays a crucial role in ammonia assimilation/reassimilation (117. 118). GS inhibition by phosphinothricin causes accumulation of toxic levels of ammonia. Since ammonia production is increased by photorespiration and conversion of nitrite to ammonia (also light-dependent), nitrogen fertilizers and light act to promote phosphinothricin efficacy (119). 

Walker, J.B., 1995, Enzymatic synthesis of aminocyclitol moieties of aminoglycoside antibiotics from inositol by Streptomyces spp. Detection of glutamine-aminocyclitol aminotransferase and diaminocyclitol aminotransferase activities in a spectinomycin producer. J. Bacteriol. 177 818-822. 

---