Thermal Activation of Actomyosin Mg‐ATPases from Ordinary and Dark Muscles of Tuna and Sardine

摘要

ABSTRACTChanges in activities of actomyosin, acto‐heavy meromyosin (acto‐HMM), and acto‐subfragment‐I (acto‐S‐I) ATPases from tuna and sardine due to heat treatment (20°, 25°, 30°, 35°, 40°C) were compared for ordinary muscle and dark muscle. Activation of ordinary muscle actomyosin Mg‐ATPases was more than doubled for tuna and tripled for sardine by heating at 35°C, while activation of dark muscle actomyosin was not observed at any temperature. The occurrence of thermal activation corresponded to a rapid loss of the EDTA‐ATPase activity. Activation of hybrid actomyosins from dark and ordinary muscles was dependent upon myosin. For acto‐HMM and acto‐S‐I thermal activation was not observed. The role of myosin tail fragments in ther