FIG. 6.

Effect of 2KG on P. putida MAD2 and its derivatives. The upper scheme summarizes the port(s) of entry of 2KG into the ED metabolic route. By virtue of the two key enzymes of the kgu cluster (encoded by PP3376 and PP3378 in P. putida), 2KG can originate 2-dehydrogluconate phosphate and 2-dehydro-3-deoxygluconate, which in turn are able to produce 6-phosphogluconate and 2-dehydro-3-deoxygluconate phosphate (Fig. 2) and further metabolized through the ED pathway. The plate tests at the lower left show the growth of various mutants of P. putida MAD2 with 2KG as the only C source. Note that excepting the eda mutant, which grows very slowly, all of the others can metabolize 2KG well. At the lower right is a C source inhibition test of P. putida MAD2 with 10 mM 2KG in the medium. Note the repressive effect of this compound on the activity of the Pu-lacZ fusion. β-gal, β-galactosidase; U. Miller, Miller units; wt, wild type.