Dual action of 2-decynoyl coenzyme A: inhibitor of hepatic mitochondrial trans-2-enoyl coenzyme A reductase and peroxisomal bifunctional protein and substrate for the mitochondrial beta-oxidation system.
The present study was designed to determine the action of the 2-acetylenic acid thioester on mitochondrial fatty acid chain elongation and beta-oxidation. Addition of 2-decynoyl CoA to a rat liver mitochondrial suspension resulted in a significant stimulation of the rate of oxidation of NADPH and NADH. This enhanced oxidation rate was not due to the mitochondrial trans-2-enoyl CoA reductase-catalyzed conversion of the 2-acetylenic acid thioester to the saturated product, decanoate, as measured by gas-liquid chromatography. On the contrary, the mitochondrial trans-2-enoyl CoA reductase activity was markedly inhibited by the 2-acetylenic acid derivative, as evidenced by the decrease in the reduction of trans-2-decenoyl CoA to decanoic acid. Incubation of the mitochondrial fraction with either NADPH or NADH and 2-decynol CoA resulted in the gas chromatographic identification of three products: beta-ketodecanoate, beta-hydroxydecanoate, and trans-2-decenoate. In the absence of reduced pyridine nucleotide, a single product was formed and identified as beta-ketodecanoate. Confirmation of the identity of this product was obtained by the observation of the formation of the Mg2+-enolate complex (303-nm absorbance peak). These results suggest that, although the 2-decynoyl CoA is an inhibitor of mitochondrial trans-2-enoyl CoA reductase activity, it is a substrate for the mitochondrial trans-2-enoyl CoA hydratase (crotonase). This was confirmed by incubation of 2-decynoyl CoA with commercially purified liver mitochondrial crotonase. The beta-ketodecanoate is formed in a two-step process: hydration of the 2-decynoyl CoA to an unstable enol intermediate which undergoes rearrangement to the beta-ketodecanoyl CoA. Interestingly, although the mitochondrial crotonase can utilize the 2-acetylenic acid thioesters, this was not the case for the peroxisomal bifunctional hydratase which was markedly inhibited by varying concentrations of 2-decynoyl CoA.
Nagi
M N
MN
Department of Pharmacology, University of Connecticut Health Center, Farmington 06032.
Cook
L
L
Laguna
J C
JC
Cinti
D L
DL
D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000037:antagonists & inhibitors*; D000214:Acyl Coenzyme A / Q000494:pharmacology*; D044944:Acyl-CoA Dehydrogenases; D000429:Alcohol Oxidoreductases / Q000378:metabolism; D000818:Animals; D002384:Catalysis; D004746:Enoyl-CoA Hydratase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D044943:Fatty Acid Desaturases / Q000037:antagonists & inhibitors*; D006836:Hydro-Lyases / Q000037:antagonists & inhibitors*; D007535:Isomerases; D008297:Male; D008830:Microbodies / Q000201:enzymology*; D008862:Microsomes, Liver / Q000378:metabolism; D008930:Mitochondria, Liver / Q000201:enzymology* / Q000378:metabolism; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors*; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D063994:Peroxisomal Bifunctional Enzyme; D051381:Rats; D011919:Rats, Inbred Strains; D013379:Substrate Specificity
D000214:Acyl Coenzyme A; D009097:Multienzyme Complexes; D009243:NAD; C050158:dec-2-ynoyl-coenzyme A; D009249:NADP; D000429:Alcohol Oxidoreductases; D015094:3-Hydroxyacyl CoA Dehydrogenases; C023744:acetoacetyl-CoA reductase; D044943:Fatty Acid Desaturases; D044944:Acyl-CoA Dehydrogenases; C100154:acyl-CoA dehydrogenase (NADP+); D006836:Hydro-Lyases; D004746:Enoyl-CoA Hydratase; D063994:Peroxisomal Bifunctional Enzyme; D007535:Isomerases