EFFECT OF CRYOPROTECTANTS AND A REDUCING REAGENT ON THE STABILITY OF ACTOMYOSIN DURING ICE STORAGE

The stability of actomyosin from carp during ice storage was studied f ocusing on the effect of disulfide bond formation on the protein confo rmational change. Behavior of characteristics of the protein in the pr esence of cryoprotectants and a reducing reagent during ice storage wa s investigated by measuring SH content, Ca2+-ATPase activity and surfa ce hydrophobicity, and by performing SDS-PAGE. In the case of no addit ives, a decrease in SH content and a dimer formation of myosin heavy c hain (MHC) through SS bonding were observed along with a decrease in C a2+-ATPase activity and an increase in surface hydrophobicity. The dim er formation of MHC proceeded even in the presence of cryoprotectants, although the Ca2+-ATPase activity was stabilized throughout ice stora ge. In addition, a slight change in surface hydrophobicity was also ob served. On the other hand, the addition of a reducing reagent (dithiot hreitol) showed that the decrease in Ca2+-ATPase activity and the incr ease in surface hydrophobicity occurred without the dimer formation of MHC through SS bonding. Therefore, it was suggested that the oxidatio n of SH groups in myosin heavy chain and the MHC dimer formation by SS bonding proceed regardless of the conformational change of myosin hea d portion related to Ca2+-ATPase activity during ice storage.