title: Amino acid residues essential for catalysis by peptidyl dipeptidase-4 from Pseudomonas maltophilia.
abstract: To assess residues essential for catalysis by prokaryotic peptidyl dipeptidase-4, the enzyme was subjected to chemical modification by a series of reagents. Treatment with either tetranitromethane or N-acetylimidazole abolished catalytic activity. Hydroxylamine reversed inactivation by acetylimidazole only. Thus, an essential tyrosine is indicated. Enzymatic activity also was quenched by either trinitrobenzenesulfonic acid or diethyl pyrocarbonate. Inactivation by these reagents was not reversed by hydroxylamine. These data suggest an essential lysine. The competitive inhibitor Phe-Arg protected partially against inactivation by tetranitromethane, and fully against inactivation by N-acetylimidazole. The substrate Hip-Phe-Arg protected against inactivation by trinitrobenzenesulfonic acid and diethyl pyrocarbonate. Thus, both tyrosine and lysine are located at the catalytic site.
authors.affiliation: New England Medical Center Hospital, Department of Medicine, Boston, MA 02111.
authors.forename: J J
authors.initials: JJ
authors.lastname: Lanzillo
authors.forename: Y
authors.initials: Y
authors.lastname: Dasarathy
authors.forename: B L
authors.initials: BL
authors.lastname: Fanburg
mesh_terms: D000595:Amino Acid Sequence; D002384:Catalysis; D004047:Diethyl Pyrocarbonate / Q000494:pharmacology; D018819:Dipeptidyl Peptidase 4; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007700:Kinetics; D011549:Pseudomonas / Q000201:enzymology*; D013379:Substrate Specificity; D013774:Tetranitromethane / Q000494:pharmacology; D014302:Trinitrobenzenesulfonic Acid / Q000494:pharmacology
chemical_list: D014302:Trinitrobenzenesulfonic Acid; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D018819:Dipeptidyl Peptidase 4; D013774:Tetranitromethane; D004047:Diethyl Pyrocarbonate