PanB is involved in nicotine metabolism in Pseudomonas putida

A nicotine-sensitive mutant was generated from the nicotine-degrading bacterium, Pseudomonas putida strain J5, by mini-Tn5 transposon mutagenesis. This mutant was unable to grow with nicotine as the sole carbon source but could grow with glucose. Sequence analysis showed that the Tn5 transposon inserted at the site of the ketopantoate hydroxymethyltransferase gene (panB), which had 54% identity to PanB in Escherichia coli K-12. In-frame deletion of the panB gene abolished the nicotine-degrading ability of strain J5, while complementation with panB from P. putida J5 and E. coli K-12 restored the degrading activity of the mutant to the wild-type level. These results suggest that ketopantoate hydroxymethyltransferase is a crucial enzyme in nicotine metabolism in P. putida J5.