Enzymatic properties of glyceraldehyde-3-phosphate dehydrogenase from fish muscle

Abstract

1. 1. Glyceraldehyde-3-phosphate dehydrogenase was isolated from the ordinary muscle of red sea bream Pagrus major, Pacific mackerel Scomber japonicus and carp Cyprinus carpio by ammonium sulfate fractionation, followed by DEAE-Sepharose CL-6B and DEAE-cellulose column chromatography and Sephadex G-150 gel filtration, and examined for enzymatic properties. 2. 2. Their optimum pH values in the backward reaction ranged from 7.8 to 8.2 and K m values from 1.56 to 1.90 mM. 3. 3. Irrespective of the species of fish, the enzymatic activity was non-competitively inhibited by inorganic phosphate in the backward reaction. 4. 4. Divalent metal ions were not necessary to activate these glyceraldehyde-3-phosphate dehydrogenases. In the presence of 1 mM Zn 2+, these enzymes showed relative activities of 42–64% the activities measured in the absence of those ions. 5. 5. Thermal stability of carp enzyme was higher than those of red sea bream and Pacific mackerel; the enzyme activity of the latter two species was almost lost on incubation at 45°C for 10–20 min, whereas carp enzyme retained half the activity even when incubated at 60°C for 30 min.