Objective: Azurocidin is an important inflammatory mediator and considered to be an inactive serine protease homologue. It has previously been reported that azurocidin is a possible IGFBP-1 specific protease; however, the protease-activity of azurocidin was not isolated in its active form. The aim of this study was to determine the effect of neutrophil-derived azurocidin on the six different IGFBPs, focusing especially on IGFBP-1.
Methods: IGFBPs were incubated with azurocidin in phosphate-buffered saline for 2 h and proteolysis was studied by SDS-PAGE. Analysis of azurocidin was performed by MALDI-TOF peptide mass fingerprint and MALDI-TOF/TOF peptide sequencing.
Results: The neutrophil-derived preparation of azurocidin cleaved IGFBP-1, IGFBP-2 and IGFBP-4. IGFBP-1 bound to IGF-I was also degraded whereas IGF-II was shown to have an inhibitory effect on proteolysis of IGFBP-1. The proteolytically active preparation of neutrophil-derived azurocidin was found to be glycosylated and determined to be 31 kDa by SDS-PAGE.
Conclusions: Our results indicate that the neutrophil-derived preparation of azurocidin contains a protease activity which cleaves IGFBP-1, IGFBP-2 and IGFBP-4. These findings are of interest since both IGFBP-1 and azurocidin increase during inflammation. The effect of azurocidin on IGFBP- and IGF-activity needs to be further investigated.
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