Toluene degradation pathway from Pseudomonas putida F1: substrate specificity and gene induction by 1-substituted benzenes

The metabolism of n-alkylbenzenes (C-3-C-7), biphenyl, styrene and cumene b y the tod pathway from Pseudomonas putida F1 was examined in terms of catab olism by the pathway enzymes and the inducibility of the tod operon. F1 cel ls grown on toluene exhibited oxygen consumption in the presence of the com pounds examined. Toluene dioxygenase (TDO) catalyzed the formation of monol , cis-dihydrodiol and triol metabolites from the n-alkylbenzenes tested and the triol formed from n-propylbenzene was metabolized to the derivative, 2 -hydroxy-6-oxohexa-2,4-dienoate (HOHD), by subsequent enzymes in the fod pa thway. Biotransformation of the tested compounds with toluene-grown F1 cell s resulted in the accumulation of ring cleavage HOHD derivatives; the metab olites were inefficiently metabolized by cell extracts of toluene-grown F1 cells, indicating that 6-methyl-HOHD hydrolase encoded by todF might be a d eterminant for the further degradation of the selected 1-substituted benzen es. The results obtained from enzyme activity assays and reverse transcript ion polymerase chain reaction (RT-PCR) showed that not only growth-supporti ng substrates, but also n-propylbenzene, styrene and cumene act as inducers of the tod operon.