title: Stereochemistry of proton abstraction catalyzed by lysine and ornithine omega-aminotransferases.
abstract: (6R)-L-[6-3H]Lysine and (6S)-L-[6]3H]lysine were prepared to investigate the stereochemical aspects of the reaction catalyzed by bacterial L-lysine epsilon-aminotransferase. When (6R)-L-[6-3H]lysine was used as a substrate, the tritium label was retained in the product, delta 1-piperideine-6-carboxylate. In contrast, the radioactivity from (6S)-L-[6-3H]lysine was found in the solvent. Thus, the pro-S hydrogen at the prochiral C-6 carbon of L-lysine is specifically abstracted by L-lysine epsilon-aminotransferase. The proton exchange was observed by proton nuclear magnetic resonance analysis in the reaction of bacterial L-ornithine delta-aminotransferase with L-ornithine in 2H2O. The isolated L-[5-2H]ornithine was converted to dextrorotatory 4-phthalimido[4-2H]butyrate. This indicates that L-ornithine delta-aminotransferase catalyzes the stereospecific exchange of the pro-S hydrogen at the prochiral C-5 carbon of L-ornithine with the solvent.
mesh_terms: D001665:Binding Sites; D051306:L-Lysine 6-Transaminase; D009952:Ornithine / Q000378:metabolism*; D009953:Ornithine-Oxo-Acid Transaminase / Q000378:metabolism*; D011522:Protons; D013237:Stereoisomerism; D000637:Transaminases / Q000378:metabolism*
chemical_list: D011522:Protons; D009952:Ornithine; D000637:Transaminases; D009953:Ornithine-Oxo-Acid Transaminase; D051306:L-Lysine 6-Transaminase