A glutathione-dependent formaldehyde dehydrogenase gene of symbiotic cyanobacterium Anabaena azollae

A 3.2 kb fragment of an indigenous Anabaena azollae plasmid was isolated an d fully sequenced. Sequence analysis identified an open reading frame of 11 10-bp that showed high similarity (56-71%) with glutathione dependent forma ldehyde dehydrogenase genes (gdfaldh) from various bacteria. The identity o f the gene was confirmed by expressing the gene in Escherichia coli with a pET-32 (a) vector followed by enzyme assay. Adjacent to the gdfaldh a secon d gene was detected that showed high similarity (53%) with an S-formylgluta thione hydrolase (fgh) gene from the methylotrophic bacterium Paracoccus de nitrificans. The presence of gdfaldh and fgh-like genes adjacent to each ot her may suggest that the corresponding gene products interact in a common m etabolic pathway involved in removing exogenous or endogenous formaldehyde.