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H NMR studies of substrate hydrogen exchange reactions catalyzed by L-methionine gamma-lyase

Journal Article · · Biochemistry; (United States)
DOI:https://doi.org/10.1021/bi00336a007· OSTI ID:6235430
Hydrogen exchange reactions of various L-amino acids catalyzed by L-methionine gamma-lyase (EC 4.4.1.11) have been studied. The enzyme catalyzes the rapid exchange of the alpha- and beta-hydrogens of L-methionine and S-methyl-L-cysteine with deuterium from the solvent. The rate of alpha-hydrogen exchange was about 40 times faster than that of the enzymatic elimination reaction of the sulfur-containing amino acids. The enzyme also catalyzes the exchange reaction of alpha- and beta-hydrogens of the straight-chain L-amino acids which are not susceptible to elimination. The exchange rates of the alpha-hydrogen and the total beta-hydrogens of L-alanine and L-alpha-aminobutyrate with deuterium followed first-order kinetics. For L-norvaline, L-norleucine, S-methyl-L-cysteine, and L-methionine, the rate of alpha-hydrogen exchange followed first-order kinetics, but the rate of total beta-hydrogen exchange decreased due to a primary isotope effect at the alpha-position. L-Phenylalanine and L-tryptophan slowly underwent alpha-hydrogen exchange. The pro-R hydrogen of glycine was deuterated stereospecifically.
Research Organization:
Kyoto Univ., Kyoto-Fu, Japan
OSTI ID:
6235430
Journal Information:
Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 15; ISSN BICHA
Country of Publication:
United States
Language:
English