Long‐chain‐acyl‐CoA synthetase activities in peroxisomes and microsomes from rat liver

Abstract

e have investigated the palmitic acid (cl6: o) and cerotic acid (c26: o) activating activities in rat-her microsomes and peroxisomes. The activation of the two fatty acids showed similar dependencies on ATP and coenzyme A, reflected in about equal apparent K, values both in microsomes and peroxisomes. In microsomes and peroxisomes similar apparent K, values for palmitic acid were found (15 pM and 22.8 pM, respectively), whereas apparent K, values for cerotic acid were 8.4 pM and 1 .O pM in microsomes and peroxisomes, respectively. The activation of cerotic acid was found to be inhibited to a progressively greater extent by increasing concentrations of 1-pyrenedecanoic acid (P10) as compared to the activation of palmitic acid, both in microsomes and peroxisomes. The inhibition by P10 of palmitic acid activation and cerotic acid activation was non-competitive in both organelles. From the observation that PI0 activation is not affected by palmitic acid and cerotic acid, we conclude that PI0 is activated by a distinct enzyme. Furthermore, our results are in accordance with earlier suggestions that activation of cerotic acid is brought about by an enzyme distinct from the palmitoyl-CoA synthetase.Mammalian cells contain a number of different fatty acid :CoA ligases (alternatively called acyl-CoA synthetases) capable of activating a variety of fatty acids to their corresponding acyl-coenzyme A esters (see [l] for review). Despite intensive research over the last few years there are differences of opinion about many aspects of fatty acid activation. With regard to the activation of long-chain fatty acids, it is clear that mitochondria, endoplasmic reticulum and peroxisomes contain ATP-dependent long-chain-acyl-CoA synthetase activity [2 -41. This activity is membrane-bound in all three organelles and the active sites of the enzymes face the cytosol in the case of the endoplasmic reticulum and peroxisomes [4, 51. The mitochondria1 long-chain-acyl-CoA synthetase is an integral part of the outer membrane, although its exact orientation in the membrane is disputed [6, 71. Tanaka and coworkers [8] purified the long-chain-acyl-CoA synthetase from mitochondria and microsomes of rat liver and concluded that the enzyme proteins are indistinguishable as judged by physicochemical, catalytic and immunological properties. Elaborating on this study, Miyazawa et al. [9] concluded that the peroxisomal enzyme as well is identical to the other two

Regulation of the Biosynthesis of 4,7,10,13,16,19-Docosahexaenoic Acid

“…Microsomes, peroxisomes, and mitochondria all contain an identical protein that is designated as a long chain acyl-CoA synthetase (28 -31). Microsomes and peroxisomes, but not mitochondria, also contain a second enzyme, which has not been purified, but it is designated as a very long chain acyl-CoA synthetase (32,33). If 24-carbon acyl-CoAs are hydrolyzed in the cytosol, and not reactivated by mitochondrial long chain acyl-CoA synthetase, it would be an efficient type of control to channel them to peroxisomes for activation and subsequent partial ␤-oxidation.…”

Proteins and enzymes of the peroxisomal membrane in mammals

“…If only the pristanoyl-CoA synthesized by the peroxisomal synthetase is available for/3-oxidation within the peroxisome is not known. These fatty acids have to be converted into acyl-CoA esters before being metabolized, and very-long-chain acyl-CoA synthetase (or lignoceroyl-CoA synthetase) activities, dependent on ATP and Mg 2+ [96], have been found to be present in peroxisomes [77,[97][98][99][100], as well as in microsomes, but not in mitochondria (except in [101 ]). Moreover, Bronfman and his collaborators [89,90] have reported that, in rat liver, hypolipidemic drugs such as ciprofibrate undergo activation to CoA-esters and presented results suggesting that the peroxisome proliferators of the fibrate series are activated by the non-specific longchain acyl-CoA synthetase.…”

“…Moreover, Bronfman and his collaborators [89,90] have reported that, in rat liver, hypolipidemic drugs such as ciprofibrate undergo activation to CoA-esters and presented results suggesting that the peroxisome proliferators of the fibrate series are activated by the non-specific longchain acyl-CoA synthetase. In recent years, evidence has been brought forward for the existence of a lignoceroyl-CoA synthetase distinct from the palmitoyI-CoA synthetase [74,77,83,97,99,100,[103][104][105][106][107] although this has been questioned by Khishimoto and coworkers [108]. These fatty acids have to be converted into acyl-CoA esters before being metabolized, and very-long-chain acyl-CoA synthetase (or lignoceroyl-CoA synthetase) activities, dependent on ATP and Mg 2+ [96], have been found to be present in peroxisomes [77,[97][98][99][100], as well as in microsomes, but not in mitochondria (except in [101 ]).…”

“…However, the possible role of the peroxisomal enzyme was not clarified [91] Very-long-chain acyI-CoA synthetase Very-long-chain fatty-acids, such as lignoceric (24:0) or cerotic (26:0) acids, are preferentially, and possibly exclu-sively, oxidized in peroxisomes [92][93][94][95]. It is noteworthy that the pathognomonic accumulation of very-long-chain fatty acids in X-linked adrenoleukodystrophy is due to deficiency of the peroxisomal lignoceroyl-CoA synthetase activity, whereas activation and oxidation of palmitic acid proceed normally in peroxisomes [99,102,105,106,109,110]. Current evidence suggests that it is only the CoA-ester synthetized by the peroxisomal enzyme which is available for fl-oxidation within the peroxisome [100,102].…”

X‐linked adrenoleukodystrophy: Biochemical diagnosis and enzyme defect

“…(2) There is a difference in the immunoprecipitability of the two activities . (3) The activities have different sensitivities towards detergents (Singh and Poulos, 1988) and pyrenedodecanoic acid (P10) (Lageweg et al 1991c). (4) There is a lack of competition of C26:o-CoA synthetase by C16:o and vice versa (Wanders et al 1987b).…”