Comparative Studies on Biochemical Properties of Myosins from Frozen Muscle of Marine Fishes

Abstract

The Biochemical properties of myosins prepared from the frozen muscle of a few marine fish species and tilapia (a tropical freshwater fish) have been compared.
1) For various myosin preparations ATP-sensitivity values varied between 2 and 5.
2) Skipjack tuna myosin was found to retain remarkably high Ca²⁺-ATPase specific activity, while those of yellowtail and bigeye tuna had comparatively lower values.
3) Certain effectors, such as KCl, Ca²⁺ and Mg²⁺ showed essentially the same effects on fish myosin ATPases as they do on rabbit skeletal muscle myosin.
4) The sulfhydryl group contents (moles per 5×10⁵g) were found to be 37-38 for skipjack tuna, yellowfin tuna and white marline myosins along with that of tilapia. Myosins of yellowtail and bigeye tuna were found to contain as few as 30-33 sulfhydryl groups.
5) When the relative thermo-stabilities of these myosins were compared in terms of the inactivation of Ca²⁺ATPase at 35°C, the sequence was found to be: tilapia, skipjack tuna, yellowfin tuna, white marline, bigeye tuna and yellowtail in decreasing order.
6) The ability of various fish myosins to combine with rabbit actin was determined by measuring the ATP-sensitivity and the stabilization of Ca²⁺ATPase to thermal denaturation. It was noted that myosins from tilapia, skipjack tuna, yellowfin tuna and white marline ratain fairly good actin combining ability.