Comparison of metabolic fluxes of cis-5-enoyl-CoA and saturated acyl-CoA through the beta-oxidation pathway.
The metabolic fluxes of cis-5-enoyl-CoAs through the beta-oxidation cycle were studied in solubilized rat liver mitochondrial samples and compared with saturated acyl-CoAs of equal chain length. These studies were accomplished using either spectrophotometric assay of enzyme activities and/or the analysis of metabolites and precursors using a gas chromatographic method after conversion of CoA esters into their free acids. Cis-5-enoyl-CoAs were dehydrogenated by acyl-CoA oxidase or acyl-CoA dehydrogenases at significantly lower rates (10-44%) than saturated acyl-CoAs. However, enoyl-CoA hydratase hydrated trans-2-cis-5-enoyl-CoA at a faster rate (at least 1.5-fold) than trans-2-enoyl-CoA. The combined activities of 3-hydroxyacyl-CoA dehydrogenase and 3-ketoacyl-CoA thiolase for 3-hydroxy-cis-5-enoyl-CoAs derived from cis-5-enoyl-CoAs were less than 40% of the activity for the corresponding 3-hydroxyacyl-CoAs prepared from saturated acyl-CoAs. Rat liver mitochondrial beta-oxidation enzymes were capable of metabolizing cis-5-enoyl-CoA via one cycle of beta-oxidation to cis-3-enoyl-CoA with two less carbons. However, the overall rates of one cycle of beta-oxidation, as determined with stable-isotope-labelled tracer, was only 15-25%, for cis-5-enoyl-CoA, of that for saturated acyl-CoA. In the presence of NADPH, the metabolism of cis-5-enoyl-CoAs was switched to the reduction pathway.(ABSTRACT TRUNCATED AT 250 WORDS)
Tserng
K Y
KY
Medical Research Service, Veterans Affairs Medical Center, Cleveland, USA.
Chen
L S
LS
Jin
S J
SJ
D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism; D000214:Acyl Coenzyme A / Q000378:metabolism*; D042964:Acyl-CoA Dehydrogenase; D042962:Acyl-CoA Oxidase; D000818:Animals; D004746:Enoyl-CoA Hydratase / Q000378:metabolism; D044943:Fatty Acid Desaturases / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D007536:Isomerism; D008099:Liver / Q000201:enzymology; D008930:Mitochondria, Liver / Q000201:enzymology; D063991:Mitochondrial Trifunctional Protein; D009097:Multienzyme Complexes / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism; D051381:Rats
D000214:Acyl Coenzyme A; D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D009097:Multienzyme Complexes; D009243:NAD; D009249:NADP; D010088:Oxidoreductases; D015094:3-Hydroxyacyl CoA Dehydrogenases; D044943:Fatty Acid Desaturases; D042962:Acyl-CoA Oxidase; D042964:Acyl-CoA Dehydrogenase; D063991:Mitochondrial Trifunctional Protein; D004746:Enoyl-CoA Hydratase