魚類筋肉グリコーゲン加水分解酵素の性質

抄録

The properties of glycogenolytic enzyme and α-glucosidase were examined by using the crude extracts from the ordinary muscle of five species of fish. Highest activities of both enzymes were detected in the extract from black sea bream. Optimum pH values of glycogenolytic enzyme from five species of fish ranged from 6.8 to 7.6, whereas those of α-glucosidase showed species-specificity, that is, pH 4.2-4.4 for Pacific mackerel, ayu and Japanese eel, pH 5.5 for black sea bream, and pH 6.2 for frog flounder.
Maximal activities of black sea bream enzymes were observed at 35°C for glycogenolytic enzyme and 40°C for α-glucosidase. Glycogenolytic activity fell by 50% during incubation at 20°C for 10min, whereas α-glucosidase activity retained 90% of its activity when incubated at 40°C for 10min. Km values for glycogen and ρ-nitrophenyl α-D-glucoside were 1.8% (pH 6.9) and 7.0×10^-4 M (pH 6.0), respectively. The Elution profile of glycogenolytic enzyme on Sephacryl S-200 revealed a single peak and its molecular weight was estimated to be 70, 000. On the other hand, two active peaks of α-glucosidase were observed on the gel filtration, and their molecular weights were estimated to be 100, 000 and 40, 000, respectively. Glycogenolytic activity from the black sea bream muscle was not activated by NaCl, while the enzyme was activated by 50% by 0.1mM CaC1₂.