CDNA CLONING AND EXPRESSION OF THE FLAVOPROTEIN D-ASPARTATE OXIDASE FROM BOVINE KIDNEY CORTEX

The isolation and sequencing of the complete cDNA coding for a D-aspar tate oxidase, as well as the overexpression of the recombinant active enzyme, are reported for the first time. This 2022 bp cDNA, beside the coding portion, comprises a 5' untranslated tract and the whole 3' re gion including the poly-adenylation signal and the poly(A) tail. The e ncoded protein comprises 341 amino acids, with the last three residues (-Ser-Lys-Leu) representing a peroxisomal targeting signal 1 (PTS1), hitherto unknown for this protein. The overexpression of recombinant D -aspartate oxidase was achieved in a prokaryotic system, and a soluble and active enzyme was obtained which accounted for about 10% of total bacterial protein. Comparisons with the known cDNAs for mammalian D-a mino acid oxidase, another peroxisomal enzyme, are also made. The clos e structural and functional similarities shared by these enzymes at th e protein level are not reflected at the nucleic acid level.