Cathepsin K: a cysteine protease with unique kinin-degrading properties

• Published in: Biochemical journal Vol. 383; no. Pt. 3; pp. 501 - 506
• Main Authors: Godat, Emmanuel, Lecaille, Fabien, Desmazes, Claire, Duchêne, Sophie, Weidauer, Enrico, Saftig, Paul, Brömme, Dieter, Vandier, Christophe, Lalmanach, Gilles
• Format: Journal Article
• Language: English
• Published: England Portland Press Ltd 01.11.2004
• Subjects: Animals; Bradykinin - metabolism; Bronchi - enzymology; Bronchi - pathology; Cathepsin K; Cathepsins - deficiency; Cathepsins - genetics; Cathepsins - metabolism; Cells, Cultured; Cysteine Endopeptidases - metabolism; Fibroblasts - cytology; Fibroblasts - enzymology; Fluorescence; Humans; Hypoxia - enzymology; Hypoxia - pathology; In Vitro Techniques; Kinins - metabolism; Mice; Mice, Inbred C57BL; Mice, Knockout; Molecular Mimicry - physiology; Muscle, Smooth - enzymology; Peptides - metabolism; Rats; Rats, Wistar
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/BJ20040864

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 Gly4-Phe5 bond and the bradykinin-mimicking substrate Abz (o-aminobenzoic acid)-RPPGFSPFR-3-NO2-Tyr (3-nitrotyrosine) more efficiently (pH 6.0: kcat/K(m)=12500 mM(-1) x s(-1); pH 7.4: kcat/K(m)=6930 mM(-1) x s(-1)) than angiotensin-converting enzyme hydrolysed BK. Conversely Abz-RPPGFSPFR-3-NO2-Tyr was not cleaved by the Y67L (Tyr67-->Leu)/L205A (Leu205-->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 Hoe140, 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.