PHYTANIC ACID ALPHA-OXIDATION IN PEROXISOMAL DISORDERS - STUDIES IN CULTURED HUMAN FIBROBLASTS

We studied the alpha-oxidation of phytanic acid in human fibroblasts o f controls and patients affected with classical Refsum disease, rhizom elic chondrodysplasia punctata, generalized peroxisomal disorders and peroxisomal bifunctional protein deficiency. Cultured fibroblasts were incubated with phytanic acid, after which medium and cells were colle cted separately. 2-Hydroxyphytanic acid and pristanic acid were measur ed in the medium and cells by stable isotope dilution gas chromatograp hy mass spectrometry, In controls, 2-hydroxyphytanic acid and pristani c acid could be detected in the medium after incubation with phytanic acid, proving that alpha-oxidation of phytanic acid via 2-hydroxyphyta noyl-CoA to pristanic acid was active and intermediates were excreted into the medium. In cells from patients with a defective alpha-oxidati on (Refsum disease, rhizomelic chondrodysplasia punctata and generaliz ed peroxisomal disorders) 2-hydroxyphytanic acid and pristanic acid we re low or not detectable, showing that in these disorders the hydroxyl ation of phytanoyl-CoA to 2-hydroxyphytanoyl-CoA is deficient. In cell s with a peroxisomal beta-oxidation defect, 2-hydroxyphytanic acid and pristanic acid were formed in amounts comparable to those in the cont rols. (C) 1997 Elsevier Science B.V.