Thermal denaturation and autolysis profiles of myofibrillar proteins of mantle muscle of jumbo squid Docidicus gigas

Jumbo squid was very similar to Japanese common squid in terms of myofibrillar Ca2+‐, Mg2+‐ and K+(EDTA)‐ATPase activities. Myofibrils of jumbo squid were significantly stabilized upon addition of Ca2+ and destabilized by increasing KCl concentration for heating. Incubation of muscle homogenate of jumbo squid induced a selective cleavage of myosin into two major fragments and the cleavage was inhibited by EDTA. Autolysis was prominent at and above 0.3 M NaCl where myosin filaments dissolve. The enzyme involved in the autolysis was proved to be unstable showing maximal autolysis rate at 25°C. Washing the homogenate partially reduced the autolysis activity.