NYMC Faculty Publications
Substrate Specificity of Human Glutamine Transaminase K as an Aminotransferase and as a Cysteine S-Conjugate Beta-Lyase
First Page
72
Last Page
81
Document Type
Article
Publication Date
6-1-2008
Department
Biochemistry and Molecular Biology
Abstract
Rat kidney glutamine transaminase K (GTK) exhibits broad specificity both as an aminotransferase and as a cysteine S-conjugate beta-lyase. The beta-lyase reaction products are pyruvate, ammonium and a sulfhydryl-containing fragment. We show here that recombinant human GTK (rhGTK) also exhibits broad specificity both as an aminotransferase and as a cysteine S-conjugate beta-lyase. S-(1,1,2,2-Tetrafluoroethyl)-l-cysteine is an excellent aminotransferase and beta-lyase substrate of rhGTK. Moderate aminotransferase and beta-lyase activities occur with the chemopreventive agent Se-methyl-l-selenocysteine. l-3-(2-Naphthyl)alanine, l-3-(1-naphthyl)alanine, 5-S-l-cysteinyldopamine and 5-S-l-cysteinyl-l-DOPA are measurable aminotransferase substrates, indicating that the active site can accommodate large aromatic amino acids. The alpha-keto acids generated by transamination/l-amino acid oxidase activity of the two catechol cysteine S-conjugates are unstable. A slow rhGTK-catalyzed beta-elimination reaction, as measured by pyruvate formation, was demonstrated with 5-S-l-cysteinyldopamine, but not with 5-S-l-cysteinyl-l-DOPA. The importance of transamination, oxidation and beta-elimination reactions involving 5-S-l-cysteinyldopamine, 5-S-l-cysteinyl-l-DOPA and Se-methyl-l-selenocysteine in human tissues and their biological relevance are discussed.
Recommended Citation
Cooper, A. J., Pinto, J. T., Krasnikov, B. F., Niatsetskaya, Z. V., Han, Q., Li, J., et al. (2008). Substrate specificity of human glutamine transaminase K as an aminotransferase and as a cysteine S-conjugate beta-lyase. Archives of Biochemistry and Biophysics, 474(1), 72-81. doi:10.1016/j.abb.2008.02.038
Publisher's Statement
Originally published in Archives of Biochemistry and Biophysics. https://doi.org/10.1016/j.abb.2008.02.038
Comments
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