The nucleotide sequence reported in this paper has been submitted to the DDBJ W GenBank W EBI Data Bank with the accession number AB049341. 1 Aureobacterium luteolum was recently renamed Microbacterium luteolum [Takeuchi, M. and Hatano, K., Int. J. Syst. Bacteriol., 48, 739-747 (1998)]. Pyridoxine 4-oxidase (EC 1.1.3.12, PN 4-oxidase), which catalyzes the oxidation of PN by oxygen or other hydrogen acceptors to form pyridoxal and hydrogen peroxide or reduced forms of the acceptors,

more »

... was puriˆed for theˆrst time to homogeneity from Microbacterium luteolum YK-1 (=Aureobacterium luteolum YK-1). 1 The puriˆed enzyme required FAD for its catalytic activity and stability. The enzyme was a monomeric protein with the subunit molecular mass of 53,000±1,000 Da. PN was the only substrate as the hydrogen donor. Oxygen, 2,6-dichloroindophenol, and vitamin K 3 were good substrates as the hydrogen acceptor. The gene ( pno) encoding PN 4-oxidase was cloned. The gene encodes a protein of 507 amino acid residues corresponding to the molecular mass of the subunit. PN 4-oxidase was expressed in Escherichia coli and found to have the same properties as the native enzyme from M. luteolum YK-1. Comparisons of primary and secondary structures with other proteins showed that the enzyme belongs to the GMC oxidoreductase family. M. luteolum YK-1 has four plasmids. The pno gene was found on a chromosomal DNA. Search for genes similar in sequence in other organisms suggested that a nitrogen-ˆxing symbiotic bacterium, Mesorhizobium loti, which harbors two plasmids, has a PN degradation pathway I in chromosomal DNA.