Peroxisomal fatty acid beta-oxidation in relation to the accumulation of very long chain fatty acids in cultured skin fibroblasts from patients with Zellweger syndrome and other peroxisomal disorders.

Abstract

The peroxisomal oxidation of the long chain fatty acid palmitate (C16:0) and the very long chain fatty acids lignocerate (C24:0) and cerotate (C26:0) was studied in freshly prepared homogenates of cultured skin fibroblasts from control individuals and patients with peroxisomal disorders. The peroxisomal oxidation of the fatty acids is almost completely dependent on the addition of ATP, coenzyme A (CoA), Mg2+ and NAD'.However, the dependency of the oxidation of palmitate on the concentration of the cofactors differs markedly from that of the oxidation of lignocerate and cerotate.The peroxisomal oxidation of all three fatty acid substrates is markedly deficient in fibroblasts from patients with the Zellweger syndrome, the neonatal form of adrenoleukodystrophy and the infantile form of Refsum disease, in accordance with the deficiency of peroxisomes in these patients. In fibroblasts from patients with X-linked adrenoleukodystrophy the peroxisomal oxidation of lignocerate and cerotate is impaired, but not that of palmitate. Competition experiments indicate that in fibroblasts, as in rat liver, distinct enzyme systems are responsible for the oxidation of palmitate on the one hand and lignocerate and cerotate on the other hand. Fractionation studies indicate that in rat liver activation of cerotate and lignocerate to cerotoyl-CoA and lignoceroyl-CoA, respectively, occurs in two subcellular fractions, the endoplasmic reticulum and the peroxisomes but not in the mitochondria. In homogenates of fibroblasts from patients lacking peroxisomes there is a small (25%) but significant deficiency of the ability to activate very long chain fatty acids. This deficient activity of very long chain fatty acyl-CoA synthetase is also observed in fibroblast homogenates from patients with X-linked adrenoleukodystrophy. We conclude that X-linked adrenoleukodystrophy is caused by a deficiency of peroxisomal very long chain fatty acyl-CoA synthetase.

Alkyl-Dihydroxyacetonephosphate Synthase

“…Cell Culture-Fibroblasts were cultured and harvested by gentle trypsinization and washing by low speed centrifugation as described before (22). The NALD patient with an isolated PTS1 import deficiency (complementation group 2 of the Kennedy Krieger Institute or group 4 of the Amsterdam nomenclature) has been described before (7).…”

X‐linked adrenoleukodystrophy: Biochemical diagnosis and enzyme defect

“…This leads to the conclusion that there must be a separate synthetase reacting preferentially with very long-chain fatty acids. Other arguments in favour of a distinct VLCFA-CoA synthetase are: (1) The subcellular localization of C26:o-CoA synthetase (in peroxisomes and microsomes) is different from that of CI6:0-CoA synthetase (in peroxisomes, microsomes and mitochondria) (Singh et al 1987;Wanders et al 1987b). (2) There is a difference in the immunoprecipitability of the two activities .…”

Peroxisomal Fatty Acid β-Oxidation in Relation to Adrenoleukodystrophy

“…In the case o f VLCFA activation occurs by a distinct synthetase located in the peroxisomal membrane. The enzyme is also present in the endoplasmic reticulum [19][20][21]. Available evidence [21] suggests that the two enzymes possess distinct functions in the cell, the perox isomal enzyme generating VLCFA-CoA esters for P-oxi dation in the peroxisome and the microsomal enzyme providing CoA esters for incorporation in cholesterol esters, triglycerides etc.…”

“…[44] that X-ALD fibroblasts were able to oxidize the CoA esters o f lignoceric acid (C24:0) at normal rates led these authors to conclude that the primary defect in X-ALD is a defi cient capacity to activate VLCFA to their CoA esters. Measurement o f this activity in total homogenates of fibroblasts, however, revealed that it was abundantly active in X-ALD fibroblasts [20]. This apparent paradox was resolved by the finding that activation of VLCFA occurs not only in peroxisomes but also in microsomes [19][20][21] and that only the peroxisomal very-long-chain fatty acyl-CoA synthetase is deficient in X-ALD [45,46].…”