Isomerization of trans-2,.DELTA.5-Dienoyl-CoA's to .DELTA.3,.DELTA.5-Dienoyl-CoA's in the .beta.-Oxidation of .DELTA.5-Unsaturated Fatty Acids

Abstract

The NADPH-dependent reduction pathway for the metabolism of delta 5-unsaturated fatty acids involves the isomerization of trans-2,delta 5-dienoyl-CoA, initially formed from the dehydrogenation of delta 5-enoyl-CoA, to isomeric delta 3,delta 5-dienoyl-CoA. The latter intermediates were then isomerized to trans-2,trans-4-dienoyl-CoA, which then follows the NADPH-dependent pathway mediated by 2,4-dienoyl-CoA reductase. The isomerization from trans-2,delta 5-dienoyl-CoA to delta 3,delta 5-dienoyl-CoA is catalyzed by delta 3,delta 2-enoyl-CoA isomerase. In this investigation, we identified the stereoisomers of delta 3,delta 5-dienoates that were formed in the reaction. Starting from trans-2,cis-5-decadienoyl-CoA, the isomerization produced cis-3,cis-5- and trans-3,cis-5-decadienoates. On the other hand, trans-2,trans-5-decadienoyl-CoA yielded cis-3,trans-5- and trans-3,trans-5-decadienoates. In addition to purified rat liver delta 3,delta 2-enoyl-CoA isomerase, acyl-CoA oxidase from Arthrobacter also catalyzed the isomerization from trans-2,cis-5-dienoyl-CoA. However, this acyl-CoA oxidase could not catalyze the similar isomerization of trans-2,trans-5-dienoyl-CoA. delta 3,delta 5-t-2,t-4-Dienoyl-CoA isomerase used cis-3,cis-5-, trans-3,cis-5-, and cis-3,trans-5-dienoyl-CoA's as substrates and converted them to trans-2,trans-4-dienoyl-CoA. In contrast, trans-3,trans-5-dienoyl-CoA was not a substrate for this isomerization. Extensive purification of acyl-CoA oxidase through column chromatography could not remove or diminish the isomerization activity associated with acyl-CoA oxidase. Acyl-CoA oxidases derived from Candida and rat liver also possess isomerization activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction pathway of cis-5 unsaturated fatty acids in intact rat-liver and rat-heart mitochondria: assessment with stable-isotype-labelled substrates

“…Two isomerases, e.g. ∆$,∆#-enoyl-CoA isomerase and ∆$ ,& -t2,t4-dienoyl-CoA isomerase, are needed for the operation of the reduction pathway of cis-5 fatty acids [3][4][5][6][7][8]. In heart mitochondria, the activities of both isomerases are higher than those in liver mitochondria [5].…”

“…The ions m/z 233 and 236 were analysed for studies with cis-5-dodecenoyl-CoA and dodecanoyl-CoA as substrates. Oxidation of an equal mixture of cis-4-decenoyl-CoA and [3,4,5,[6][7][8][9][10][11][12][13] C 4 ]decanoyl-CoA in rat-liver and rat-heart mitochondria 3OHMC10 was the major metabolite detected in the incubation of an equal mixture of cis-4-decenoyl-CoA and [3,4,5,6-"$C % ]decanoyl-CoA in rat-liver and rat-heart mitochondria. As shown in Table 2, the concentration of 3OHMC10 was significantly increased after rotenone treatment in both liver and heart mitochondria.…”

“…As well as the conventional isomerase-mediated pathway [1], the oxidation of cis-5 unsaturated fatty acids also uses reduction pathways that are dependent on NADPH [2]. The major reduction pathway is postulated to mediate through the dehydrogenation of cis-5-enoyl-CoA to trans-2,cis-5-dienoyl-CoA, which is then isomerized to cis-3,cis-5-and trans-3,cis-5-dienoyl-CoAs as shown in Scheme 1 [3][4][5][6][7][8]. This isomerization is catalysed by ∆$,∆#-enoyl-CoA isomerase or peroxisomal tri-functional enzyme [3,5].…”

“…The existence of the reduction pathway is well established from the study of mitochondrial enzyme extracts [3][4][5][6][7]. In the absence of exogenous NADPH, metabolic intermediates, such as trans-2,trans-4-dienoate and ∆$ ,& -dienoates, accumulate [2,3,[5][6][7].…”

“…3,4,5,6-"$C % ]decanoyl-CoA and 3OHMC14 produced from [3,4,5,6-"$C % ]tetradecanoyl-CoA, this fragment contained only one "$C label on C-3. Therefore m\z 233 and 234 were monitored for mj0 Correlation between mj0 enrichment (%) derived from the monitoring of m/z 233 (mj0) and 234 (mj1), and m/z 317 (mj0) and 321 (mj4) ion pairs for 3OHMC10 produced from the incubation of equal amounts of unlabelled cis-4-decenoyl-CoA and[3,4,5,[6][7][8][9][10][11][12][13] C 4 ]decanoyl-CoA in rat-liver mitochondriaThe correlation coefficient (r ) was 0.9967. The regression line was Y l 1.08 (p0.04) Xk2.95 (p1.77).…”