GENETIC-STRUCTURE OF THE BPHG GENE ENCODING 2-HYDROXYMUCONIC SEMIALDEHYDE DEHYDROGENASE OF ACHROMOBACTER-XYLOSOXIDANS KF701

2-Hydroxymuconic semialdehyde dehydrogenase catalyzes the conversion o f 2-hydroxymuconic semialdehyde (HMS) to an enol form of 4-oxalocroton ate which is a step in the catechol meta-cleavage pathway. A bphG gene encoding HMS dehydrogenase of A. xylosoxidans KF701, a soil bacterium degrading biphenyl, was identified at between catechol 2,3-dioxygenas e gene and HMS hydrolase gene, and its sequence was analyzed. An open reading frame (ORF) corresponding to bphG gene was consisted of 1461 n ucleotides with ATG initiation codon and TGA termination codon. The OR F exhibited 66% of G + C content, and a putative ribosome-binding sequ ence, AGAGA, was identified at about 10 nucleotides upstream initiatio n codon of the bphG gene. The bphG gene can encode a polypeptide of mo lecular weight 52 kDa containing 486 amino acid residues. A deduced am ino acid sequence of HMS dehydrogenase encoded in bphG gene from A. xy losoxidans KF701 exhibited the highest 94% homology with that of corre sponding enzyme encoded in xylG from P. putida mt-2, 63% to 90% homolo gy with those of other reported HMS dehydrogenases, and 29% to 42% hom ology with those of betaine aldehyde dehydrogenase, 5-carboxy-HMS dehy drogenase, aldehyde dehydrogenase, indole-3-acetaldehyde dehydrogenase , succinic semialdehyde dehydrogenase, methylmalonate semialdehyde deh ydrogenase, and succinylglutamate 5-semialdehyde dehydrogenase. From a n alignment of amino acid sequence of HMS dehydrogenase from A. xyloso xidans KF701 with other reported dehydrogenases, putative cofactor NAD (+)-binding regions and catalytic residues were identified. (C) 1998 A cademic Press.