title: Syntheses and kinetic evaluation of racemic and optically active 2-benzyl-2-methyl-3,4-epoxybutanoic acids as irreversible inactivators for carboxypeptidase A.
abstract: Racemic and optically active 2-benzyl-2-methyl-3,4-epoxybutanoic acids were synthesized and evaluated as inactivators for carboxypeptidase A, a representative zinc-containing proteolytic enzyme. Only the threo-form of the inactivator is effective and its potency in terms of k(inact)/K(I) value is lower by 42-fold compared with 2-benzyl-3,4-epoxybutanoic acid, indicating that the alpha-methyl group affects adversely in the inactivation contrary to the expectation that it would enhance the inactivation activity of the inhibitor through additional interactions of the methyl group with a small cavity (alpha-methyl hole) present next to the S1' hydrophobic pocket. Of the enantiomeric pair, the inactivator having the (2S,3R)-configuration is more potent than its enantiomer by 44-fold. The observed kinetic results may be rationalized on the basis that the methyl group in the inactivator having the (2R,3S)-configuration experiences the van der Waals repulsive interactions with the bottom of the active site crevice in binding to CPA, casting a doubt on the presence of the so-called alpha-methyl hole at the active site of carboxypeptidase A.
authors.affiliation: Division of Molecular and Life Sciences and Center for Integrated Molecular Systems, Pohang University of Science and Technology, San 31 Hyojadong, 790-784, Pohang, Republic of Korea.
authors.forename: Mijoon
authors.initials: M
authors.lastname: Lee
authors.forename: Dong H
authors.initials: DH
authors.lastname: Kim
mesh_terms: D000818:Animals; D001665:Binding Sites; D002087:Butyrates / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D002268:Carboxypeptidases / Q000037:antagonists & inhibitors*; D043422:Carboxypeptidases A; D002417:Cattle; D004791:Enzyme Inhibitors / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D004852:Epoxy Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D007700:Kinetics; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors; D011485:Protein Binding; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D002087:Butyrates; D004791:Enzyme Inhibitors; D004852:Epoxy Compounds; D002268:Carboxypeptidases; D043422:Carboxypeptidases A; D008666:Metalloendopeptidases