title: Inhibition and active-site modelling of prolidase.
abstract: Consideration of the active-site model of prolidase led us to examine azetidine, pyrrolidine and piperidine substrate analogs as potential in vivo inhibitors of the enzyme. One of these, N-benzyloxycarbonyl-L-proline, was shown to be a potent competitive inhibitor of porcine kidney prolidase (Ki = 90 microM); its rapid protein-mediated permeation of human and sheep erythrocytes suggests that it may be effective in vivo. The higher homolog, N-benzyloxycarbonyl-L-pipecolic acid, was also a potent inhibitor of the enzyme while the antihypertensive drugs, captopril and enalaprilat, were shown to have mild and no inhibitory effects, respectively. Analysis of inhibitor action and consideration of X-ray crystallographic data of relevant Mn2+ complexes allowed the active-site model of prolidase to be further refined; a new model is presented in which the substrate acts as a bidentate ligand towards the active-site manganous ion. Various aspects of the new model help to explain why Mn2+ has been 'chosen' by the enzyme in preference to other biologically available metal ions.
authors.affiliation: Department of Biochemistry, University of Sydney, Australia.
authors.forename: G F
authors.initials: GF
authors.lastname: King
authors.forename: M J
authors.initials: MJ
authors.lastname: Crossley
authors.forename: P W
authors.initials: PW
authors.lastname: Kuchel
mesh_terms: D000818:Animals; D001384:Azetidines / Q000494:pharmacology; D001665:Binding Sites; D004150:Dipeptidases / Q000037:antagonists & inhibitors*; D004912:Erythrocytes / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D008958:Models, Molecular; D015394:Molecular Structure; D010880:Piperidines / Q000494:pharmacology; D011480:Protease Inhibitors / Q000097:blood / Q000494:pharmacology*; D011759:Pyrrolidines / Q000494:pharmacology; D012756:Sheep; D013329:Structure-Activity Relationship; D013552:Swine
chemical_list: D001384:Azetidines; D010880:Piperidines; D011480:Protease Inhibitors; D011759:Pyrrolidines; D004150:Dipeptidases; C022449:proline dipeptidase