Cloning and Structural Analysis of the Genes for Peroxisomal β-Oxidation Enzymes

Summary

cDNAs and genes of peroxisomal β-oxidation enzymes, acyl-CoA oxidase, enoyl-CoA:hydratase-3-hydroxyacyl-CoA dehydrogenase bifunctional enzyme, and 3-ketoacyl-CoA thiolase, were cloned and analyzed. The sizes of the mRNAs for these enzymes were estimated by blotting analysis to be 3.8, 3.0, and 1.9 kilobases, respectively. Two species of acyl-CoA oxidase cDNAs were found, which are different in their sequences only in a small region. The corresponding mRNAs were shown to be produced by alternative use of two separate exons in the splicing process. Both forms of the mRNAs encode proteins of 661 amino acids, whose primary structures are partially different. The sequences of the two exons are significantly related to each other, suggesting that they were produced by an exon duplication. The bifunctional enzyme consists of 721 amino acids, excluding the initiator methionine. Its amino-terminal and carboxy-terminal portions have significant sequence homology to mitochondrial enoyl-CoA hydratase and 3-hydroxyacyl-CoA dehydrogenase, respectively, representing the positions of the two functions on the bifunctional enzyme polypeptide.