Peroxisomal beta-oxidation of polyunsaturated long chain fatty acids in human fibroblasts. The polyunsaturated and the saturated long chain fatty acids are retroconverted by the same acyl-CoA oxidase.

The metabolism of the C22 unsaturated fatty acids erucic acid (22:1(n-9)), adrenic acid (22:4(n-6)), docosapentaenoic acid (22:5(n-3)) and docosahexaenoic acid (22:6(n-3)) was studied in cultured fibroblasts from patients with acyl-CoA oxidase deficiency, the Zellweger syndrome, X-linked adrenoleukodystrophy (X-ALD) and normal controls. [3-14C] 22:4 (n-6) and [3-14C] 22:5 (n-3) were shortened (retroconverted) to [1-14C] 20:4 (n-6) and [1-14C] 20:5 (n-3), respectively, in normal and X-ALD fibroblasts. In Zellweger and acyl-CoA oxidase deficient fibroblasts these reactions were deficient. Since the retroconversion is normal in X-ALD fibroblasts peroxisomal very long chain (lignoceryl) CoA ligase is probably not required for the activation of C22 unsaturated fatty acids. The present work with fibroblasts from patients with a specific acyl-CoA oxidase deficiency, previously shown to have a deficient peroxisomal clofibrate-inducible acyl-CoA oxidase, and which accumulate 24:0 and 26:0 fatty acids, supports the view that this enzyme is responsible for the chain-shortening of docosahexaenoic acid (22:6(n-3)), erucic acid (22:1(n-9)), docosapentaenoic acid (22:5(n-3)), and adrenic acid (22:4(n-6)) as well.