Human fibroblast tissue inhibitor of metalloproteinases: glycosylation and function

The glycosylation of human fibroblast tissue inhibitor of metalloproteinases and procollagenase was examined in vivo using tunicamycin B2 and in vitro using Peptide: N-glycosidase F. In the presence of tunicamycin B2, unglycosylated inhibitor continues to be synthesized and secreted at normal or increased rates. The protein core of this collagenase inhibitor has an apparent Mr of 21,000 and possesses at least two oligosaccharide linkage sites as evidenced by the accumulation of a single 25,000 dalton intermediate. Collagenase inhibitor deglycosylated by Peptide: N-glycosidase also has an apparent molecular weight of 21,000 daltons; furthermore, deglycosylated inhibitor continues to block the activity of collagenase at a 1:1 molar stoichiometry and does not differ from the native glycoprotein in its resistance to tryptic degradation. Using these same two reagents, the characteristic doublet of human fibroblast procollagenase was found to result from glycosylation in the upper (60,000 dalton) form. Secretion of procollagenase was significantly inhibited in the presence of tunicamycin B2.