Calprotectin inhibits matrix metalloproteinases by sequestration of zinc

Background/Aimss-Calprotectin, a 36 kDa protein present in neutrophil cytop lasm, has antimicrobial and apoptosis inducing activities, which are revers ed by the addition of zinc. Matrix metalloproteinases (MMPs), a family of z inc dependent enzymes, are important in many normal biological processes in cluding embryonic development, angiogenesis, and wound healing, but also pa thological processes such as inflammation, cancer, and tissue destruction. The aim of this study was to investigate whether calprotectin can inhibit M MP activity, and whether such inhibition could be overcome by the addition of zinc. Methods-MMP activity was measured by the degradation of substrates precoate d on to microwells, and visualised by Coomassie blue staining of residual s ubstrate. Seven metalloproteinases (MMP-1, MMP-2, MMP-3, MMP-7, MMP-8, MMP- 9, and MMP-13) were teste against two substrates: gelatin and alpha -casein . Results-All MMPs except MMP-1 were active against gelatin, whereas MMP-7 wa s the only enzyme active against alpha -casein. The addition of calprotecti n inhibited the activity of all the MMPs, but different concentrations of t he protein, from 0.3 muM to > 11 muM, were necessary to produce a 50% inhib ition of the MMPs. Inhibition by calprotectin was largely overcome by the a ddition of zinc. Conclusions-The findings suggest that calprotectin inhibits MMPs by sequest ration of zinc. The data also suggest that MMPs have different affinities f or zinc and that calprotectin has a lower zinc affinity than the MMPs.