抄録
When carp myosin was stored in ice, a decrease in SH content and polymerization of myosin heavy chain (MHC) through SS bonding were observed along with a decrease in Ca2+-ATPase activity. By adding a chelating reagent (EDTA), the decrease in SH content and the polymerization were depressed. The addition of a reducing reagent (dithiothreitol) showed that the decrease in Ca2+-ATPase activity occurredwithout the polymerization by SS bonding. In contrast, the polymerization of MHCwas greatly promoted in the presence of a metal ion (Cu2+), whereas the decreasein Ca2+-ATPase activity was observed at the same level as without the metal ion. The addition of cryoprotectants (sorbitol, sucrose) showed a slight depressing effect on the decrease in Ca2+-ATPase activity and noinfluence on the polymerization of MHC.
It was concluded that the oxidation of SH groups in myosin along withthe polymerization of MHC proceeded regardless of the conformational change in myosin head portion related to Ca2+-ATPase activity during ice storage. Therefore, it was suggested that the MHC polymerization during ice storage is due to SH groups on the myosin tail portion, even if myosin is free from actin.
