The mouse gene PDCR encodes a peroxisomal Δ²,Δ⁴-dienoyl-CoA reductase

Here we describe the identification and characterization of a novel mouse gene, PDCR, that encodes a peroxisomal Δ²,Δ⁴-dienoyl-CoA reductase. The mouse PDCR cDNA contains an 892-base pair open reading frame and is predicted to encode a 292-amino acid protein with a deduced molecular mass of 31,298 Da that terminates in a consensus type-1 peroxisomal targeting signal. Purified recombinant PDCR protein was generated from Escherichia coli and catalyzed the NADPH-dependent reduction of Δ²-trans,Δ⁴-trans-decadienoyl- CoA with a specific activity of 20 units/mg. Enzymatic characterization followed by high pressure liquid chromatography analysis of the products revealed that PDCR converted Δ²-trans,Δ⁴-trans-decadienoyl-CoA to a Δ³- enoyl-CoA but not to a Δ²-enoyl-CoA. Kinetic analyses demonstrated that PDCR is active on a broad range of Δ²,Δ⁴-dienoyl-CoAs. Although the observed substrate preference was to Δ²-trans,Δ⁴-trans-decadienoyl-CoA, PDCR was also active on a C₂₂ substrate with multiple unsaturations, a result consistent with the role of peroxisomes in the oxidation of complex, very long chain, polyunsaturated fatty acids. The presence of a type-1 peroxisomal targeting signal Ala-Lys-Leu-COOH at the C terminus of PDCR suggested that this protein may be peroxisomal. We observed that tagged PDCR was efficiently transported to the peroxisome lumen in normal human fibroblasts but not in cells derived from a Zellweger syndrome patient with a specific defect in peroxisomal matrix protein import. We conclude that this protein resides within the peroxisome matrix and therefore represents the first mammalian peroxisomal Δ²,Δ⁴-dienoyl-CoA reductase to be characterized at the molecular level.