Comparative properties of three functionally different but structurally related serpin variants from horse plasma.
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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.
SUBMITTER: Potempa J
PROVIDER: S-EPMC1150162 | biostudies-other | 1991 Mar
REPOSITORIES: biostudies-other
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