Activation of long chain fatty acids by subcellular fractions of rat liver: III. Effect of ethylenic bond position on acyl‐CoA formation ofcis‐octadecenoates

Abstract

The rates of rat liver microsomal and mitochondrial activation of the Δ4 to Δ17cis‐octadecenoate positional isomers have been investigated. The fatty acid to protein ratios required for maximum activation of the Δ8, Δ9 and Δ10 isomers were much lower than the corresponding ratios required for maximum activation of thecis‐octadecenoates with double bonds at either end of the fatty acid molecule. Also, as the incubation temperature was raised from 22–38 C the Δ8 and Δ9 isomers exhibited little change in their rates of activation, while large increases in activation rates of the isomers with the double bond at either end of the fatty acid chain were observed. Differential inhibition of the activation of the various positional isomers was observed when anionic, cationic, or nonionic detergents were included in the incubation medium. The different responses to fatty acid concentration, temperature and detergents are attributed to enzyme specificity and to differences in solution properties of thecis‐octadecenoates, rather than to the presence of separate rat liver enzymes that catalyze acyl‐CoA ester formation of the various positional isomers.

Long‐chain Fatty Acid:CoA Ligase in Rat Brain in vitro: A Comparison of Activities with Oleic and cis‐Vaccenic Acids

“…We were particularly interested in comparing activities of oleic (18:l[n-9]) and cis-vaccenic (18:l[n-7]) acids, since data from earlier studies in this laboratory had suggested that these naturally occurring isomers are handled differently by the ligase (Murphy and Spence, 1977). Our present finding, that the maximum reaction rate with cis-vaccenic acid exceeded that with oleate, is consistent with the observations of Lippel et al (1973). Using rat-liver microsomes, these investigators demonstrated a 50-60% difference in relative ligase activities (cisvaccenate > oleate) at high levels of fatty acid.…”

“…The reaction properties observed in this study for the brain ligase are similar to those reported for the liver enzyme in several respects. These include the sharp peak in activity around pH 8.5 (Bar-Tana et al, 1971;Pande, 1972;Lippel et al, 1973;Polokoff and Bell, 1977), an apparent K,,, of 2 mM for ATP (Polokoff and Bell, 1977), and almost total dependence on ATP as nucleotide (Bar-Tana et al, 1971;Polokoff and Bell, 1977). At 6 p~, the apparent K,,, for CoASH for the brain ligase is within the range of values reported for the liver enzyme (Groot et al, 1976).…”

Dissimilar Properties of Vaccenic Versus Elaidic Acid in β‐Oxidation Activities and Gene Regulation in Rat Liver Cells

“…Activation of NEFAs by CoA is a prerequisite before the carnitine-dependent activities allow acyl chains to cross the mitochondrial inner membranes. Comparable acyl-CoA synthetase activities with the four isomers in the presence of responsible organelles fully support previous results obtained with cis- [38] and trans- [39] isomers under other experimental conditions. This suggests that CPT I was provided, through our experimental procedures, with equal amounts of C 18:1 -CoA isomers.…”