title: Influence of divalent and monovalent cations on some active site properties of human factor Xa.
abstract: The effect of divalent and monovalent cations on the hydrolysis of BzIleGlu(OR)GlyArgpNA(S-2222) was compared to the rate of inactivation of factor Xa by dansyl-GluGlyArg-chloromethylketone(DERG-CK). At substrate concentrations below Km, an approximate four-fold increase in amidase activity was observed in the presence of manganese ions while a three-fold increase was observed with calcium ions. The presence of magnesium ions resulted in a two-fold increase in amidase activity. Similar increases in the rate of inactivation of factor Xa by DERG-CK were observed. Na+ ions had a marked enhancing effect of both factor Xa amidase activity and inactivation by DERG-CK. Kinetic parameters for the hydrolysis of S-2222 by factor Xa were obtained in the presence and absence of Ca++ and Na+. Vmax values increased in the presence of either Ca++ or Na+. Km values increased in the presence of Ca++ while there was a modest decrease in Km in the presence of Na+. It is suggested that the enhanced activity of factor Xa is a reflection of changes in the reactivity of active site residues.
authors.affiliation: Dental Research Center, School of Dentistry, University of North Carolina at Chapel Hill 27599-7455.
authors.forename: D T
authors.initials: DT
authors.lastname: Manly
authors.forename: G L
authors.initials: GL
authors.lastname: Featherstone
authors.forename: J W
authors.initials: JW
authors.lastname: Jenzano
authors.forename: H R
authors.initials: HR
authors.lastname: Roberts
authors.forename: R L
authors.initials: RL
authors.lastname: Lundblad
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D001665:Binding Sites / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology*; D002414:Cations, Monovalent / Q000494:pharmacology*; D003619:Dansyl Compounds; D015951:Factor Xa; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D009842:Oligopeptides / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors; D012964:Sodium / Q000494:pharmacology
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D002413:Cations, Divalent; D002414:Cations, Monovalent; D003619:Dansyl Compounds; D009842:Oligopeptides; D015842:Serine Proteinase Inhibitors; D008345:Manganese; C015608:benzoyl-Ile-Glu-Gly-Arg-p-nitroanilide; C030824:dansylglutamyl-glycyl-arginine chloromethyl ketone; D008094:Lithium; D012964:Sodium; D012697:Serine Endopeptidases; D015951:Factor Xa; D008274:Magnesium; D011188:Potassium; D002118:Calcium