Effect of CaCl2 on Water-holding Capacity of Alaska Pollack Myofibrils and on Their Thermal Stability

Alaska pollack myofibrils were suspended or dissolved in the media containing varied con-centrations of CaCl2 and NaCl conferring different ionic strengths, and the water-holding capacity (WHC) of myofibrils and thermal inactivation rate (KD)of myofibrillar Ca-ATPase were studied. A large decrease in WHC of myofibrils was found to occur when the ionic strength (I) of medium remained low (I=0.05-0.10) and CaCl2 was further added to the medium at the con-centration of less than 15mM. When CaCl2 was added to the myofibrils in the media of various ionic strength, khe KD was increascd several times by the addition of CaCl2 regardlless of the ionic strength of the media. After removal of CaCl2 by dialysis, F-actin was added to the myofibrils with an equal amount of myosin content in it. The KD was nearly recovered and equal to that of the untreated myofibrils with CaCl2. It was thus suggested that the actin portion in the myofibrils of alaska pollack was domi-nantly denatured through the reaction with CaCl2.