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Maria Rapala-Kozik, Jan Potempa, Daniel Nelson, Andrzej Kozik, James Travis

Comparative Cleavage Sites within the Reactive-Site Loop of Native and Oxidized ?1-Proteinase Inhibitor by Selected Bacterial Proteinases

Human ?₁-proteinase inhibitor (?₁-PI) is responsible for the tight control of neutrophil elastase activity which, if down regulated, may cause local excessive tissue degradation. Many bacterial proteinases can inactivate ?₁-PI by hydrolytic cleavage within its reactive site, resulting in the down regulation of elastase, and this mechanism is likely to contribute to the connective tissue damage often associated with bacterial infections. Another pathway of the inactivation of ?₁-PI is reversible and involves oxidation of a critical active-site methionine residue that may influence inhibitor susceptibility to proteolytic inactivation. Hence, the aim of this work was to determine whether this oxidation event might affect the rate and pattern of the cleavage of the ?₁-PI reactive-site loop by selected bacterial proteinases, including thermolysin, aureolysin, serralysin, pseudolysin, Staphylococcus aureus serine proteinase, streptopain, and periodontain. A shift of cleavage specificity was observed after ?₁-PI oxidation, with a preference for the Glu³⁵⁴-Ala³⁵⁵ bond by most of the proteinases tested. Only aureolysin and serralysin cleave the oxidized form of ?₁-PI faster than the native inhibitor, suggesting that bacteria which secrete these metalloproteinases may specifically take advantage of the host defense oxidative mechanism to accelerate elimination of ?₁-PI and, consequently, tissue degradation by neutrophil elastase.

Biological Chemistry, Walter de Gruyter

Print ISSN: 1431-6730
Volume: 380, 10/1999
Pages: 1211 - 1216

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