The depolymerising action of pepsin on collagen molecular weights of the component polypeptide chains

Abstract

Molecular weight studies have been carried out on the polypeptide chains released by thermal denaturation of collagen pretreated with pepsin. Tropocollagen yields a component, α∗, with molecular weight approx. 95 000, this component has a slightly lower weight than α. Pepsin digestion of polymerised collagen fibrils releases some α∗ and some higher-molecular weight components. The ease with which α∗ is formed from these fibrils is greatest in collagen from young tissues and becomes progressively more difficult with age. Since aged collagen after pepsin digestion, yields up to 50% hot soluble gelatin and a readily detectable amount of tyrosyl peptides3, it is suggested that during maturation covalent cross-linkages are introduced, some of which are resistant to pepsin digestion and these latter prevent the solubilisation of single α∗ components. Even though many cross-linkages may be broken, sufficient remain which are resistant to pepsin resulting in an insoluble residue and high-molecular weight gelatin being formed.