title: Substrate-dependent, non-hyperbolic kinetics of pig brain prolyl oligopeptidase and its tight binding inhibition by JTP-4819.
abstract: Prolyl oligopeptidase (POP) is a cytosolic serine protease that hydrolyses small peptides at the carboxyl end of the proline residue. It has raised pharmaceutical interest, since its inhibitors have been shown to have antiamnesic properties. We studied prolyl oligopeptidase kinetics with two 7-amino-4-methylcoumarin derivatives: Z-Gly-Pro-AMC and Suc-Gly-Pro-AMC. Z-Gly-Pro-AMC was found to obey standard Henri-Michaelis-Menten kinetics with a K(m) of 30+/-3 microM, whereas Suc-Gly-Pro-AMC exhibited substrate inhibition kinetics with K(m) and K(is) of 510+/-150 and 270+/-90 microM, respectively. Autodock simulations revealed that either the succinyl or the AMC-end of Suc-Gly-Pro-AMC may bind to the S'1 subsite of the active site. We believe that non-specifically bound Suc-Gly-Pro-AMC allows the simultaneous binding of second substrate molecule to the active site and this leads in substrate inhibition. In addition, we demonstrated that the inhibition type of a well characterized prolyl oligopeptidase inhibitor, JTP-4819, is competitive tight binding with a K(ic) of 0.045+/-0.008 nM. We suggest that due to the high concentration of prolyl oligopeptidase in the brain (0.12 nmol/g pig brain), the tight binding nature of the inhibition should be considered when using brain homogenate as the enzyme source in prolyl oligopeptidase inhibition measurements. This is of importance in studying structure-activity relationships of potent prolyl oligopeptidase inhibitors.
authors.affiliation: Department of Pharmacology and Toxicology, University of Kuopio, P.O. Box 1627, FIN-70211, Kuopio, Finland. jarkko.venalainen@uku.fi
authors.forename: Jarkko I
authors.initials: JI
authors.lastname: Venäläinen
authors.forename: Risto O
authors.initials: RO
authors.lastname: Juvonen
authors.forename: Markus M
authors.initials: MM
authors.lastname: Forsberg
authors.forename: Arturo
authors.initials: A
authors.lastname: Garcia-Horsman
authors.forename: Antti
authors.initials: A
authors.lastname: Poso
authors.forename: Erik A A
authors.initials: EA
authors.lastname: Wallen
authors.forename: Jukka
authors.initials: J
authors.lastname: Gynther
authors.forename: Pekka T
authors.initials: PT
authors.lastname: Männistö
mesh_terms: D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000187:drug effects* / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D007700:Kinetics; D000085822:Prolyl Oligopeptidases; D011480:Protease Inhibitors / Q000494:pharmacology*; D011759:Pyrrolidines / Q000494:pharmacology*; D012697:Serine Endopeptidases / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D013552:Swine
chemical_list: D011480:Protease Inhibitors; D011759:Pyrrolidines; C094211:JTP 4819; D012697:Serine Endopeptidases; D000085822:Prolyl Oligopeptidases