Identification of the peroxisomal beta-oxidation enzymes involved in the degradation of leukotrienes.

Leukotrienes (LTs) are metabolically inactivated via omega-oxidation and subsequent beta-oxidation from the omega-end. This beta-oxidation process takes place in peroxisomes. In this study we investigated the role of different enzymes involved in peroxisomal beta-oxidation in the degradation of LTs. We analyzed LTB(4), LTE(4), and their oxidation products in urine of patients with Infantile Refsum's disease (IRD), d-bifunctional protein (DBP) deficiency, Rhizomelic Chondrodysplasia Punctata (RCDP) type 1, and X-linked adrenoleukodystrophy (XALD). We found that patients with IRD and DBP deficiencies excrete increased amounts of LTB(4), LTE(4), omega-carboxy-LTB(4), and omega-carboxy-LTE(4) in their urine, whereas the beta-oxidation products were not detectable. These results show that DBP plays an essential role in the degradation of LTs. In urine of patients with XALD and RCDP type 1 we found normal levels of LTB(4), LTE(4), and their oxidation products, indicating that the adrenoleukodystrophy protein and peroxisomal 3-ketoacyl-CoA thiolase are not involved in the metabolic inactivation of LTs.

Excretion of 3,6-epoxydicarboxylic acids in peroxisomal disorders.

The urinary excretions of several organic acids were quantitatively studied by gas chromatography/mass spectrometry in subjects with disorders of peroxisome biogenesis (n = 8) and controls (n = 26). The excretion of 3,6-epoxtetradecanedioic acid was significantly elevated in all subjects with disorders of peroxisome biogenesis (1.8-20.8; controls, not detected-0.5, mumol/mmol of creatinine). 3,6-Epoxydodecanedioic acid excretion was usually elevated (1.4-19.8; controls, not detected-4.2) and 3,6-epoxyoctanedioic acid excretion was not elevated not detected-8.8; controls, 0.6-9.5 mumol/mmol of creatinine). It is suggested that measurement of 3,6-epoxydicarboxylic acids may be useful for the diagnosis of these disorders.

Urinary dicarboxylic acids in X-linked adrenoleukodystrophy.

The urinary excretion of dicarboxylic acids in X-linked adrenoleukodystrophy (X-ALD) was studied. The dicarboxylic acid profile in X-ALD did not show any specific pattern, unlike Zellweger syndrome and neonatal adrenoleukodystrophy. Medium-chain dicarboxylic acids with an even number of carbon atoms (adipic, suberic, sebacic) and an odd number of carbon atoms (pimelic, azelaic) were excreted within the normal ranges. Dicarboxylic acids with more than 10 carbon atoms were not found. These findings may be due to the normal beta-oxidation system of dicarboxylic acids in X-ALD.

Mass spectrometric identification of 2-hydroxy-sebacic acid in the urines of patients with neonatal adrenoleukodystrophy and Zellweger syndrome.

The urines of children with neonatal adrenoleukodystrophy and Zellweger syndrome contained an excess of unusual even- and odd-numbered dicarboxylic acids with a chain length of from 5 to 15 carbon atoms, as well as 2-hydroxy-compounds, including 2-hydroxy-isocaproate, 2-hydroxy-glutarate and 2-hydroxy-sebacate. The latter product, not previously found in metabolic diseases, appears as an additional useful marker of these peroxisomal disorders.

Medium- and long-chain dicarboxylic aciduria in patients with Zellweger syndrome and neonatal adrenoleukodystrophy.

This study reports that patients with neonatal adrenoleukodystrophy and Zellweger syndrome excrete a very peculiar pattern of organic acids. Dicarboxylic acids with an even number of carbon atoms (adipic, suberic, sebacic, 2- and 3-hydroxy-sebacic, hexadecanedioic), as well as with an odd number of carbon atoms (pimelic, azelaic, un-, tri-, and pentadecanedioic) were found in excess in the urines of six patients with neonatal adrenoleukodystrophy and one with Zellweger syndrome. The accumulation of dicarboxylic acids, reflecting an impairment of their beta-oxidation in mitochondria and/or peroxisomes, thus appears as an additional useful marker of these peroxisomal diseases.