The participation of soluble factors in the ω‐oxidation of fatty acids in the liver of the sheep

Abstract

The removal of soluble components from an ovine hepatic microsomal preparation decreased the omega-hydroxylation of dodecanoic and hexadecanoic acids. The results suggest that one or more soluble components play a role in the microsomal omega-hydroxylation of fatty acids. The possible roles in the reaction of catalase (known to stimulate the microsomal desaturations of fatty acids and alkylglycerols) and superoxide dismutase were investigated. The addition of these enzymes to the complete (but not the washed) microsomal preparation stimulated both the initial omega-hydroxylation reaction and the subsequent dehydrogenation reactions of the omega-oxidation pathway. The similarity of the effects of catalase and superoxide dismutase and stimulation of two different steps of the omega-oxidation pathway suggest that these agents are acting indirectly by removing active oxygen species rather than directly on the enzymes of microsomal fatty acid omega-hydroxylation.

The effect of cytosol on liver microsomal metabolic activation and demethylation of N-nitrosodimethylamine

“…With increased amounts of added cytosol, we saw decreased formaldehyde production, consistent with the observations of Hong and Yang (7). There is a precedent for the involvement of cytosolic proteins in enhancing reactions catalyzed by cytochrome P450, with proposed mechanisms including suppression of lipid peroxidation or facilitation of the P450 reactions through enhancing substrate binding, participating in electron transfer, or stabilizing components of the P450 complex (30)(31)(32)(33). We have found no evidence for a role for lipid peroxidation (Table 7).…”