Studies on Metabolism of Fatty Acid in Fish-II : Cofactors Effecting β-Oxidation System of Fatty Acid in Carp Hepatopancreas Mitochondria

Some properties of the β-oxidation system in carp (Cyprinus carpio) dark muscle mitochondria were studied with octanoate as the substrate, and compared with those in carp hepatopancreas mitochondria. It was observed that the O2 uptake based on the, β-oxidation system in dark muscle was 330 μl/mg of mitochondria-N/60 min, and the activity of this system was higher than that in hepatopancreas. The β-oxidation system was similar to that in hepatopancreas, suggesting that the activation of fatty acids and the permeation of the activated acids through the membrane are probably the initial stages of the β-oxidation phenomenon. The role of α-ketoglutarate, a TCA cycle intermediate, as a sparker in endogenous respiration and β-oxidation was the same as in hepatopancreas. The optimum pH of this enzymatic system was pH 8.0, and the optimum temperature was 25°C. Investigating O2 uptake based on the α-oxidation system in dark muscle and hepatopancreas, it was found that the contribution of dark muscle to β-oxidation was more important than that of hepatopancreas. However it may be further concluded that the capacity of fatty acid oxidation in fish is inferior to that in mammalia. The discoloration of dark muscle resulted in a decrease in O2 uptake based on the, β-oxidation system.