Glutamine transaminase

Jones TW, Chen Q, Schaeffer V, et al. 1988. Immunohistochemical localization of glutamine transaminase K, a rat kidney cysteine conjugate p-lyase, and the relationship to the segment specificity of cysteine conjugate nephrotoxicity. Mai Pharm 34 621-627. 

At pH 7.5 less than 1% of the compound exists in the open-chain a-keto-acid form while at pH 9 approximately 3% is in a form that reacts as a typical a-keto acid. Glutamine transaminase also catalyzes the transamination of glutamic acid y-A -methylamide the expected transamination product, a-keto-A-methylglutaramic acid has not yet been isolated from a transamination reaction mixture. However, this compound was... 

Reliable enzymatic assays for SeMet are not available as specific SeMet metabolizing enzymes have not been identified and enzymes such as glutamine transaminase react with Met equally as well as with SeMet (Blazon et al., 1994). However, with some enzymes reaction rates for SeMet and Met differ sufficiently to be of some use in SeMet analysis. For example, SeMet is a better substrate than Met for the a,y-elimination by i.-methionine y-lyase of Pseudomonas putida (Esaki et al., 1979). The adenosyl methionine transferase from rat liver reacts with L-SeMet at 51% of the rate with L-Met, and with the corresponding D-isomers at only 13 and 10% of the rate of L-Met (Pan and Tarver, 1967). Other adenosyl methionine transferases, such as that from yeast, react with SeMet more rapidly and with higher stereoselectivity than with Met, providing an indirect means for SeMet determination (Mudd and Cantoni, 1957 Sliwkowski, 1984 Uzar and Michaelis, 1994). 

Recently it has been established that pyridazines can be formed by enzymic catalysis. For example, pyridazinones are formed from y-glutamyl hydra-zones of a-keto acids in the presence of liver glutamine transaminase, or from y-glutamyl hydrazide in the presence of L-amino acid oxidase. ... 

Glutamine transaminases Methionine, glutamine their a-keto acid analogs 1-4... 

New Glutamine Transaminase from Rat Kidney, J. Biol. Chem., 2554 (1974). 

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