Preparation and structural analysis of actinidain-processed atelocollagen of yellowfin tuna (Thunnus albacares)

Pepsin-hydrolyzed collagen (atelocollagen) is a trimer, consisting of alpha 1 and alpha 2 monomers, and shows molecular species corresponding to a monomer, dimer (beta chain), and trimer (gamma chain) by SDS-polyacrylamide gel electrophoresis. Atelocollagen was purified from yellowfin tuna (Thunnus albacares) by salt precipitation and cation-exchange chromatography. Enzymatic hydrolysis of the atelocollagen by actinidain, a cysteine protease purified from kiwifruit, was analyzed by SDS-polyacrylamide gel electrophoresis. The triple helical structure unique to collagen was retained in the atelocollagen as judged by circular dichroism spectra. The actinidain-processed atelocollagen showed only monomeric alpha 1 and alpha 2 chains, with no beta and gamma chains, by SDS-polyacrylamide gel electrophoresis; nevertheless, it retained the typical triple helical structure. It is suggested that actinidain cleaved the atelocollagen molecule at specific sites on the inside of the inter-strand cross-linking peptides.