Crystal structures of Citrobacter freundii methionine γ-lyase complexes with
the substrates of γ- (L-1-amino-3-methylthiopropylphosphinic acid) and β-
(S-ethyl-L-cysteine) elimination reactions and the competitive inhibitor
L-norleucine have been determined at 1.45, 1.8, and 1.63 Å resolution,
respectively. All three amino acids occupy the active site of the enzyme but do
not form a covalent bond with pyridoxal 5'-phosphate. Hydrophobic interactions
between the active site residues and the side groups of the substrates and the
inhibitor are supposed to cause noncovalent binding. Arg374 and Ser339 are
involved in the binding of carboxyl groups of the substrates and the inhibitor.
The hydroxyl of Tyr113 is a potential acceptor of a proton from the amino groups
of the amino acids.
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