Mechanistic studies on lysine 2,3-aminomutase: carbon-13—deuterium crossover experiments

Abstract

A mixture of L-[3,3-²H₂]lysine plus L-[2-¹³C]lysine is converted by purified lysine 2,3-aminomutase into β-lysine. The di-N-phthaloyl methyl ester derivative of the resultant β-lysine shows a geminally deuterium-coupled enriched ¹³C n.m.r. signal indicating intermolecular transfer of the migrating 3-pro-R hydrogen of the α-lysine. L-[3-¹³C]Lysine has been synthesized. A mixture of L-[3,3-²H₂]lysine plus L-[3-¹³C]lysine is similarly converted into β-lysine. Its di-N-phthaloyl methyl ester derivative shows a β-shifted enriched ¹³C n.m.r. signal for C-3, but no geminally coupled enriched C-3 signal. The latter experiment rules out any intermolecular exchange of the non-migrating 3-pro-S hydrogen atom of α-lysine. Various mechanistic possibilities for the intermolecular hydrogen transfer process are discussed.