Isolation and identification of cryptic bioactive regions in bovine achilles tendon collagen

Several proteins are known to host specific regions within their sequence, that when exposed or excised out proteolytically can display a range of physiological activities quite different from that of the parent protein. Collagen, a class of structural biopolymers and an important component of the extracellular matrix, is now known to harbor several such bioactive peptides which can act as physiological regulators. This study was undertaken to identify such cryptic sites from bovine Achilles tendon collagen and an antioxidative assay was used to screen for bioactivity. Bacterial crude protease was used to hydrolyze collagen and the hydrolysate was subjected to separation through ion-exchange column chromatography. Fractions were screened using conventional antioxidative assays and further purified by gel permeation chromatography. Two biologically active cryptic peptides were obtained displaying high antioxidative properties, E1 and F3. At low concentrations, both peptides displayed higher chelating ability than EDTA and were able to reduce the auto-oxidation of unsaturated fatty acid. The molecular weights of the peptides were found out through column chromatography and Tricine SDS PAGE; both displayed molecular mass below 4 kDa. Overall E1 displayed a comparatively better antioxidative ability than the others and was further characterized by circular dichroism studies and sequencing. A BLAST search of the active peptide sequence revealed that an almost similar peptide also resides in human collagen Type I.