title: The p11 subunit of annexin II heterotetramer is regulated by basic carboxypeptidase.
abstract: The Ca(2+)-dependent phospholipid-binding protein annexin II heterotetramer (AIIt) is composed of two copies of annexin II and a p11 dimer. The interaction of the carboxyl-terminal lysine residues of the p11 subunit of AIIt with the lysine-binding kringle domains of plasminogen is believed to play a key role in plasminogen binding and stimulation of the tPA-catalyzed cleavage of plasminogen to plasmin. In the current report, we show that AIIt-stimulated plasminogen activation is regulated by basic carboxypeptidases, in vitro. The incubation of AIIt with a 1/400 molar ratio of carboxypeptidase B for periods as short as 2 min resulted in a significant loss in AIIt-stimulated plasminogen activation. Carboxypeptidase B (CpB) as well as thrombin-activated fibrinolysis inhibitor (TAFIa) and carboxypeptidase N (CpN) rapidly reduced AIIt-stimulated plasminogen activation by 80%. The molar ratio of carboxypeptidase/AIIt for half-maximal inhibition of AIIt was 1/4700, 1/700, and 1/500 for CpB, TAFIa, and CpN, respectively. Treatment of AIIt with carboxypeptidase resulted in loss of both carboxyl-terminal lysine residues from the p11 subunit, which correlated with a decrease in the k(cat) and an increase in the K(m) for plasminogen activation. The data reveal a novel mechanism for the regulation of AIIt-stimulated plasminogen activation.
authors.affiliation: Cancer Biology Research Group, Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Darin K
authors.initials: DK
authors.lastname: Fogg
authors.forename: David E
authors.initials: DE
authors.lastname: Bridges
authors.forename: Kitty Kit-Ting
authors.initials: KK
authors.lastname: Cheung
authors.forename: Geetha
authors.initials: G
authors.lastname: Kassam
authors.forename: Nolan R
authors.initials: NR
authors.lastname: Filipenko
authors.forename: Kyu-Sil
authors.initials: KS
authors.lastname: Choi
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Fitzpatrick
authors.forename: Michael
authors.initials: M
authors.lastname: Nesheim
authors.forename: David M
authors.initials: DM
authors.lastname: Waisman
mesh_terms: D017306:Annexin A2 / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D043424:Carboxypeptidase B; D002268:Carboxypeptidases / Q000378:metabolism*; D019281:Dimerization; D006801:Humans; D007700:Kinetics; D008024:Ligands; D008239:Lysine; D001121:Lysine Carboxypeptidase / Q000378:metabolism*; D010960:Plasminogen Activators / Q000378:metabolism; D011489:Protein Denaturation; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D010959:Tissue Plasminogen Activator / Q000737:chemistry / Q000378:metabolism
chemical_list: D017306:Annexin A2; D008024:Ligands; D021122:Protein Subunits; D011994:Recombinant Proteins; D002268:Carboxypeptidases; D043424:Carboxypeptidase B; D001121:Lysine Carboxypeptidase; D010960:Plasminogen Activators; D010959:Tissue Plasminogen Activator; D008239:Lysine