Biosynthetic processing of collagen molecules

A large number of extracellular proteins are synthesized in vivo as precursor molecules that must be proteolytically processed into their mature functional forms. Included among such proteins are a subset of the collagens. A number of the proteinases involved in the biosynthetic processing of collagen precursor molecules have fairly recently been identified and characterized. It is :now evident that the proteinases involved in processing collagen precursors are responsible for the biosynthetic processing of various other kinds of extracellular proteins as well. The result is coordination of biosynthesis of the various processed collagens, and the formation of macromolecular structures formed by some of them, with other molecular events in morphogenesis and homeostasis. In this chapter, the natures of recently characterized families of proteinases involved in collagen processing are summarized, as are recently described ancillary proteins that enhance collagen processing. Also summarized are noncollagenous substrates that have recently been demonstrated to be processed by proteinases which also process collagens and whose biosyntheses are therefore linked with collagen biosynthesis.