title: Comparative properties of three functionally different but structurally related serpin variants from horse plasma.
abstract: Three structurally related but functionally different serpins from horse plasma were isolated and characterized. In spite of their identical N-terminal sequences, which show some similarity to that of human alpha 1-proteinase inhibitor, the reactive-centre loops of each of these proteins show extensive variation. Only inhibitor I, with a P1 methionine residue, resembles human alpha 1-PI with regard to (a) similarity of amino acid sequence in the vicinity of the reactive-site peptide bond, (b) broad inhibitory specificity, (c) sensitivity to oxidative inactivation and (d) high rate of reactivity with neutrophil elastase(s). Inhibitor II, with a P1 arginine residue, is an exclusive trypsin inhibitor, and inhibitor III is an oxidation-resistant slow-reacting elastase inhibitor with a P1 alanine residue. Comparison of association rate constants for the inhibition of horse neutrophil elastases by the three inhibitors indicates that only inhibitor I is likely to be physiologically important in the regulation of these enzymes.
authors.affiliation: Institute of Molecular Biology, Jagiellonian University, Cracow, Poland.
authors.forename: J
authors.initials: J
authors.lastname: Potempa
authors.forename: J K
authors.initials: JK
authors.lastname: Wunderlich
authors.forename: J
authors.initials: J
authors.lastname: Travis
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D010450:Endopeptidases / Q000378:metabolism; D006736:Horses; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D012689:Sequence Homology, Nucleic Acid; D015843:Serpins / Q000097:blood* / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D015843:Serpins; D010450:Endopeptidases