Abstract
Activities of ω-oxidation of stearic acid in rat liver preparations were assayed at various enzyme concentrations. When 0.05 ml of postmitochondrial fraction or microsomes in the equal amount was used, it was found that there were some activators in the supernatant fraction for ω-oxidation, containing some heat stable factors and ω-hydroxystearate dehydrogenase. The optimum pH for dehydrogenase was 7.4, and the enzymic activities were higher in the supernatant fractions from alloxan diabetic rats and from starved ones than in those from control rats. When 0.4ml of the postmitochondrial fraction was used, it was revealed that ω-oxidation required the optimum concentration of NADPH for the maximum activity. In the assay system with 0.8ml of the postmitochondrial fraction, ω-oxidation activities were increased in the diabetic rats and the starved ones. These increases were dependent on the supernatant fractions. Increased incorporation of substrates to phospholipid reduced thee-oxidation activity. The substrates in phospholipid contained no polar metabolites.
Higher ω-oxidation activities in the diabetic rats and the starved ones suggest thatco-oxidation may be involved in fatty acid degradation. Dicarboxylic acid can be metabolized further by β-oxidation and finally becomes succinyl CoA. The physiological significance of ω-oxidation might consist in supplying the substrates of TCA cycle for utilization of acetyl CoA and for gluconeogenesis, especially in diabetic rats and starved ones.
