Occurrence of Glycylhydroxypyrolyl Sequences in Earthworm Cuticle Collagen

Salt-soluble collagen of earthworm cuticle contains much hydroxyproline in the second position of tripeptide sequences beginning with glycine, as determined by sequence analysis of mixed peptides released by the action of clostridial collagenase. A tripeptide, Gly-Hyp-Ala, was isolated from these digests and identified by sequence analysis and by comparison with a synthetic reference peptide. It was estimated to account for approximately 10% of the hydroxyproline of both purified salt-soluble collagen and of the total collagen of the cuticle.