致死条件が肉蛋白におよぼす影響-I
即殺および苦悶死コイのミオシン区蛋白の組成
1960 年 26 巻 2 号 p. 140-148
詳細
1960 年 26 巻 2 号 p. 140-148
In order to examine the influence of death conditions upon the muscle proteins, composition of myosins from two groups of carp was determined by salting-out analysis: one group was put to an instant death by beheading (Control Group), and the other was killed after being left in the air for several hours (Anguish Group).
Salting-out curves of myosins from the both groups were alike in that peaks in the range 30-45% (v/v) saturation of ammonium sulfate predominated, which are presumed to consist of actomyosin and myosin (Fig. 1 and 2), while, in Anguish Group, a fraction precipitating in the range 10-20% saturation was usually found, such fraction was not found generally in the Control Group (Fig. 1 and 2). This fraction is presumed to be actin, and this was ascertained by a rise of viscosity on mixing the fraction precipitating at 20% saturation and rabbit myosin (Fig. 3). It may be note worthy that actin was fractionated from natural myosins, since it has long escaped from detection by either electrophoretic or ultracentrifugal method.
If myosins were extracted with addition of ATP (1mg. per g. muscle), from the muscle of carp killed in anguish, actin fraction disappeared in the salting-out curve (Fig. 4).
This as well as the fact that the muscle from Anguish Group contains far less ATP may suggest that appearance of actin in the salting-out curve might be related to ATP content of the muscle.
Sodium pyrophosphate was found to have the same effect as ATP, so far as in causing disappearance of actin fraction in the salting-out curve of Anguish group (Fig. 5).
The results were explained by the following assumptions: (i) In muscle of carp killed in anguish, interaction between actin and myosin might become weakened. The extent of the weakening, however, might be so small as it could manifest itself only in the presence of salt in pretty high concentrations as used in the salting-out analysis. (ii) The weakening of the interaction might be due to a sort of denaturation of actin and/or myosin, induced by certain factors produced in the course of biochemical change in muscle before death. (iii) ATP in the muscle might play a role to protect the protein from denaturation.
