Characterization of the human omega-oxidation pathway for omega-hydroxy-very-long-chain fatty acids

Very-long-chain fatty acids (VLCFAs) have long been known to be degraded exclusively in peroxisomes via beta-oxidation. A defect in peroxisomal beta-oxidation results in elevated levels of VLCFAs and is associated with the most frequent inherited disorder of the central nervous system white matter, X-linked adrenoleukodystrophy. Recently, we demonstrated that VLCFAs can also undergo omega-oxidation, which may provide an alternative route for the breakdown of VLCFAs. The omega-oxidation of VLCFA is initiated by CYP4F2 and CYP4F3B, which produce omega-hydroxy-VLCFAs. In this article, we characterized the enzymes involved in the formation of very-long-chain dicarboxylic acids from omega-hydroxy-VLCFAs. We demonstrate that very-long-chain dicarboxylic acids are produced via two independent pathways. The first is mediated by an as yet unidentified, microsomal NAD(+)-dependent alcohol dehydrogenase and fatty aldehyde dehydrogenase, which is encoded by the ALDH3A2 gene and is deficient in patients with Sjogren-Larsson syndrome. The second pathway involves the NADPH-dependent hydroxylation of omega-hydroxy-VLCFAs by CYP4F2, CYP4F3B, or CYP4F3A. Enzyme kinetic studies show that oxidation of omega-hydroxy-VLCFAs occurs predominantly via the NAD(+)-dependent route. Overall, our data demonstrate that in humans all enzymes are present for the complete conversion of VLCFAs to their corresponding very-long-chain dicarboxylic acids

STUDIES ON THE SUBSTRATE-SPECIFICITY OF THE INDUCIBLE AND NONINDUCIBLE ACYL-COA OXIDASES FROM RAT-KIDNEY PEROXISOMES.

We have studied the substrate specificity of the inducible (acyl-CoA oxidase I) and non-inducible (acyl-CoA oxidase II) oxidases in peroxisome-enriched fractions from rat kidney. The two oxidases were separated by means of ion-exchange chromatography and shown to accept a variety of acyl-CoA esters as substrates, including lignoceroyl-CoA, palmitoyl-CoA, lauroyl-CoA, caproyl-CoA, and trimethyltridecanoyl-CoA. Glutaryl-CoA was found to react exclusively with the inducible enzyme, and pristanoyl-CoA exclusively with the non-inducible enzyme. We conclude that under normal non-induced conditions both acyl-CoA oxidase I and II contribute to the oxidation of the various acyl-CoA esters with the exception of pristanoyl-CoA and glutaryl-CoA, although the extent to which each enzyme contributes to the oxidation was found to differ between the various acyl-CoA esters. [on SciFinder (R)

Triesters of tris-(hydroxymethyl)phosphine oxide

A series of tri-acylated and tri-arylated tris(hydroxymethyl)phosphine oxide derivatives was prepared either from tris-(hydroxymethyl)phosphine oxide or from tris-(iodomethyl)phosphine oxide

Measurement of very long-chain fatty acids, phytanic and pristanic acid in plasma and cultured fibroblasts by gas chromatography.

Two methods are described, both currently used in our laboratory, for the quantitative analysis of very long-chain fatty acids, phytanic acid and pristanic acid in plasma and cultured fibroblasts by gas-liquid chromatography. The first method is based on the procedure developed by Moser and Moser (1991) and the second is based on the method of Onkenhout and colleagues (1989), which is an application of the original method of Lepage and Roy for plasma and fibroblasts. A survey is given of the concentrations of very long-chain fatty acids, pristanic and phytanic acid in plasma and fibroblasts from control subjects and all patients investigated so far in our laboratory.Two methods are described, both currently used in our laboratory, for the quantitative analysis of very long-chain fatty acids, phytanic acid and pristanic acid in plasma and cultured fibroblasts by gas-liquid chromatography. The first method is based on the procedure developed by Moser and Moser (1991) and the second is based on the method of Onkenhout and colleagues (1989), which is an application of the original method of Lepage and Roy for plasma and fibroblasts. A survey is given of the concentrations of very long-chain fatty acids, pristanic and phytanic acid in plasma and fibroblasts from control subjects and all patients investigated so far in our laboratory.A

2,6-dimethylheptanoyl-CoA is a specific substrate for long-chain acyl-CoA dehydrogenase (LCAD): evidence for a major role of LCAD in branched-chain fatty acid oxidation.

Oxidation of straight-chain fatty acids in mitochondria involves the complicated interaction between a large variety of different enzymes. So far four different mitochondrial straight-chain acyl-CoA dehydrogenases have been identified. The physiological function of three of the four acyl-CoA dehydrogenases has been resolved in recent years especially from studies on patients suffering from certain inborn errors of mitochondrial fatty acid beta-oxidation. The physiological role of long-chain acyl-CoA dehydrogenase (LCAD) has remained obscure, however. The results described in this paper provide strong evidence suggesting that LCAD plays a central role in branched-chain fatty acid metabolism since it turns out to be the major acyl-CoA dehydrogenase reacting with 2,6-dimethylheptanoyl-CoA, a metabolite of pristanic acid, which itself is the alpha-oxidation product of phytanic aci