N-Glycosylation pattern of the zymogenic form of human matrix metalloproteinase-9.

Glycosylation of proteins has profound consequences on the activities of macromolecules and their interactions with inhibitors/substrates. Matrix metalloproteinase-9 (MMP-9, also known as gelatinase B) is a member of the MMP family of zinc-dependent endopeptidases, with critical functions in both physiological and pathological processes. MMP-9, a glycosylated MMP, is implicated in inflammation, angiogenesis and tumor metastasis. We have determined by the use of mass spectrometry that of the three possible N-glycosylation sites in human MMP-9 only two are glycosylated. The N-glycosylation sites are at asparagines in positions 38 and 120, the first site within the propeptide domain of the zymogenic form (pro-MMP-9) of the enzyme and the second in the catalytic domain. The chemical nature of the sugar attachments to both these sites was determined by mass spectrometry. Both N-glycosylation sites have NeuAcalpha(1,2)-Galbeta(1,4)-GlcNAcbeta(1,2)-Manalpha(1,3)-[NeuAcalpha(1,2)-Galbeta(1,4)-GlcNAcbeta(1,2)-Manalpha(1,6)-]Manbeta(1,4)-GlcNAcbeta(1,4)-[Fucalpha(1,6)-]GlcNAcbeta oligosaccharide chains. A computational model of glycosylated pro-MMP-9 was generated and it was studied by dynamics simulations