Effect of pepsin digestion on two distinct types of collagen in the muscle and skin of squid Todarodes pacificus

The effect of pepsin digestion on each type of collagen from the mantle muscle, mantle skin, and arm muscle of the squid Todarodes pacificus was examined by biochemical and immunochemical techniques. An alpha chain-sized component, termed chain c, in the SDS-PAGE pattern of the residue after alkali extraction (RS-AL) was reactive for the antiseum against the alpha 1(SQ-I) component which was one of the subunits of the major collagen, Type SQ-I. The band pattern of chain c in immunoblot analysis was not changed by pepsin digestion. These results indicate that chain c is an intact form of the alpha 1(SQ-I) component with relatively small telopeptides. On the other hand, another alpha chain-sized component, named chain a, in the RS-AL was reactive for the antiserum against the alpha 1(SQ-II) component which was one of the subunits of the minor collagen. Type SO-II. Chain a had a slower mobility on SDS-PAGE than the alpha 1(SQ-II) component. Only the alpha 1(SQ-II) component was reactive for the anti-alpha 1(SQ-II) component serum in the pepsin-solubilized collagen, indicating that the alpha 1(SQ-II) component was produced from chain a by pepsin digestion. Additionally, chain a and the alpha 1(SQ-II) component showed quite similar peptide maps of V-8 protease digests to each other. These results indicated that chain a was an intact form of the alpha 1(SQ-II) component with relatively large telopeptides.