期刊
BIOCHEMICAL JOURNAL
卷 383, 期 -, 页码 501-506出版社
PORTLAND PRESS LTD
DOI: 10.1042/BJ20040864
关键词
cathepsin; cysteine protease; kinin; kininase; lung inflammation
资金
- NIAMS NIH HHS [AR46182, R01 AR046182] Funding Source: Medline
Taking into account a previous report of an unidentified enzyme from macrophages acting as a kininase, the ability of cysteine proteases to degrade kinins has been investigated. Wild-type fibroblast lysates from mice, by contrast with cathepsin K-deficient lysates. hydrolysed BK (bradykinin), and released two metabolites, BK-(1-4) and BK-(5-9). Cathepsin K, but not cathepsins B, H. L and S, cleaved kinins at the Gly(4)-Phe(5) bond and the bradykinin-mimicking substrate Abz (o-aminobenzoic acid)-RPPGFSPFR-3-NO2-Tyr (3-nitrotyrosine) more efficiently (pH 6.0: k(cat)/K-m = 12 500 mM(-1) . s(-1) ; pH 7.4: k(cat)/K-m = 6930 mM(-1) . s(-1)) than angiotensin-converting enzyme hydrolysed BK. Conversely Abz-RPPGFSPFR-3-NO2-Tyr was not cleaved by the Y67L (Tyr(67) --> Leu)/L205A (Leu(205) Ala) cathepsin K mutant, indicating that kinin degradation mostly depends on the S2 substrate specificity. Kininase activity was further evaluated on bronchial smooth muscles. BK, but not its metabolites BK(1-4) and BK(5-9), induced a dose-dependent contraction, which was abolished by Hoe 140, a B2-type receptor antagonist. Cathepsin K impaired BK-dependent contraction of normal and chronic hypoxic rats, whereas cathepsins B and L did not. Taking together vasoactive properties of kinins and the potency of cathepsin K to modulate BK-dependent contraction of smooth muscles, the present data support the notion that cathepsin K may act as a kininase, a unique property among mammalian cysteine proteases.
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