PARTIAL AMINO-ACID-SEQUENCE OF AN L-AMINO-ACID OXIDASE FROM THE CYANOBACTERIUM SYNECHOCOCCUS PCC6301, CLONING AND DNA-SEQUENCE ANALYSIS OF THE AOXA GENE

A novel type of L-amino acid oxidase from Synechococcus PCC6301 was pu rified and subjected to amino acid sequence analysis. Since the N-term inus of the L-amino acid oxidase protein was not accessible for Edman degradation, the protein was partially hydrolysed and a contiguous seq uence of 17 amino acid residues was obtained from an endogenous peptid e fragment. Based on the partial peptide sequence two oligonucleotides were designed, which were used as probes in Southern hybridization ex periments in order to identify the corresponding aoxA gene. The aoxA g ene was isolated from a size-fractionated genomic library of Synechoco ccus PCC6301 and subsequently sequenced. From the nucleotide sequence (data base accession number Z48565) it can be deduced that the L-amino acid protein consists of 355 amino acid residues resulting in a molar mass of 39.2 kDa. The calculated isoelectric point of the protein is 9.81. The L-amino acid oxidase from Synechococcus PCC6301 shows low ho mologies to other flavin oxidases/dehydrogenases, especially amine oxi dases, but no homologies to other so far sequenced L- or D-amino acid oxidases.