In this study, we isolated and characterized the acid-soluble skin collagen of Pacific bluefin tuna (PBT, Thunnus orientalis). The PBT skin collagen was composed of two α chains (α1 and α2) and one β chain. The denaturation temperature of PBT collagen was low although it was rich in proline and hydroxyproline. The primary structure of PBT skin collagen was almost identical to that of calf and salmon skin collagen
however, it differed with respect to the epitope recognition of the antibody against salmon type I collagen. These results suggest that the primary structure of skin collagen was highly conserved among animal species, although partial sequences that included the epitope structure differed among collagens.