A novel acyl-CoA oxidase that can oxidize short-chain acyl-CoA in plant peroxisomes

Short-chain acyl-CoA oxidases are beta-oxidation enzymes that are active on short-chain acyl-CoAs and that appear to be present in higher plant peroxi somes and absent in mammalian peroxisomes. Therefore, plant peroxisomes are capable of performing complete beta-oxidation of acyl-CoA chains, whereas mammalian peroxisomes can perform beta-oxidation of only those acyl-CoA cha ins that are larger than octanoyl-CoA (C-8), In this report, we have shown that a novel acyl-CoA oxidase can oxidize short-chain acyl-CoA in plant per oxisomes. A peroxisomal short-chain acyl-CoA oxidase from Arabidopsis was p urified following the expression of the Arabidopsis cDNA in a baculovirus e xpression system, The purified enzyme was active on butyryl-CoA (C-4), hexa noyl-CoA (C-6), and octanoyl-CoA (C-8), Cell fractionation and immunocytoch emical analysis revealed that the short-chain acyl-CoA oxidase is localized in peroxisomes, The expression pattern of the short-chain acyl-CoA oxidase was similar to that of peroxisomal 3-ketoacyl-CoA thiolase, a marker enzym e of fatty acid beta-oxidation, during post-germinative growth. Although th e molecular structure and amino acid sequence of the enzyme are similar to those of mammalian mitochondrial acyl-CoA dehydrogenase, the purified enzym e has no activity as acyl-CoA dehydrogenase, These results indicate that th e short-chain acyl-CoA oxidases function in fatty acid beta-oxidation in pl ant peroxisomes, and that by the cooperative action of long- and short-chai n acyl-CoA oxidases, plant peroxisomes are capable of performing the comple te beta-oxidation of acyl-CoA,