Autocatalytic processing of gamma-glutamyltranspeptidase.
gamma-Glutamyltranspeptidase is the key enzyme in glutathione metabolism, and we previously presented evidence suggesting that it belongs to the N-terminal nucleophile hydrolase superfamily. Enzymatically active gamma-glutamyltranspeptidase, which consists of one large subunit and one small subunit, is generated from an inactive common precursor through post-translational proteolytic processing. The processing mechanism for gamma-glutamyltranspeptidase of Escherichia coli K-12 has been analyzed by means of in vitro studies using purified precursors. Here we show that the processing of a precursor of gamma-glutamyltranspeptidase is an intramolecular autocatalytic event and that the catalytic nucleophile for the processing reaction is the oxygen atom of the side chain of Thr-391 (N-terminal residue of the small (beta) subunit), which is also the nucleophile for the enzymatic reaction.
Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan. hideyuki@lif.kyoto-u.ac.jp
Hideyuki
H
Suzuki
Hidehiko
H
Kumagai
D002384:Catalysis; D004926:Escherichia coli / Q000201:enzymology*; D019811:Hydroxylamine / Q000494:pharmacology; D007700:Kinetics; D016296:Mutagenesis; D011480:Protease Inhibitors / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism; D005723:gamma-Glutamyltransferase / Q000235:genetics / Q000378:metabolism*
D011480:Protease Inhibitors; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D019811:Hydroxylamine; D005723:gamma-Glutamyltransferase