Procollagen conversion

Because concanavalin A also inhibited the conversion of procollagen into collagen by carboxyl-terminal protease, it was suggested that this protease contains oligosaccharide side-chains that are recognized by concanavalin A, and that tunicamycin affects the secretion, activity, or activation of this enzyme.484... 

Conversion of procollagen to collagen requires at least two proteases a procollagen aminoprotease and a procollagen carboxyprotease. The former catalyzes removal of the N-terminal propeptide and the latter removal of the C-terminal propeptide. The two enzymes are endopepti-dases, function at neutral pH, require a bivalent cation such as Ca +, and show a preference for the helical conformation. There appears to be no preferential order for the cleavage of the propeptides. 

The conversion of procollagen to collagen by removal of propeptides seems to be essential for the formation of collagen fibrils. This supposition is supported by studies of two heritable diseases, one found in humans and the other in cattle, sheep, and cats. In both, the defect lies in the removal of N-terminal propeptides and results in impaired fibril formation. The human disorder is the type VII variant of Ehlers-Danlos syndrome (Table 25-5). Affected individuals exhibit marked joint hypermobility, dislocation of joints, short stature, and minor changes in skin elasticity. Their skin fibroblasts show normal... 

Either the pro l chains or the assembled procollagen is secreted from the cell where conversion of procollagen to collagen takes place. In this conversion, the teleopeptides are removed (27) by procollagen peptidase to reduce the size of the 1 chains to 95,000. Procollagen... 

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