Binding of Mercury Compounds to Protein Components of Fish Muscle

Abstract

The binding properties of mercury to the protein components of fish muscle were examined using the dorsal muscle of Japanese sea bass Lateolabrax japonicus.
Total mercury content in the protein components of fish muscle fractionated at 5°C was highest in the subactomyosin, followed by myofibrillar protein, actomyosin and sarcoplasmic protein. The ratio of methylmercury to total mercury was not remarkably different among the protein components. The content of reactive sulfhydryl groups decreased in the order of sacroplasmic protein, subactomyosin, myofibrillar protein and actomyosin. The content of reactive sulfhydryl groups was lower in the sarcoplasmic protein fractionated at 25°C (body temperature) than at 5°C.
When the fish muscle was incubated in 0.55M phosphate buffer containing 0.55M potassium chloride with methylmercury chloride or mercuric chloride, the affinity of protein components to the mercurials at 5°C decreased in the order of subactomyosin, sarcoplasmic protein, myofibrillar protein and actomyosin. While the affinity of myofibrillar protein to mercurials at 25°C was higher than that of the sarcoplasmic protein. For sarcoplasmic protein, the order of reactive sulfhydryl groups content differed with had the affinity to mercurials.