Key enzymes of 2,4-D and 2,4,5-T degradation from Nocardioides simplex strain 3E

The induction of maleylacetate reductase and hydroxyhydroquinone 1,2-dioxygenase was observed when Nocardioides simplex strain 3E was grown with 2,4-D. When grown with 2,4,5-T, the strain produced maleylacetate reductase and two dioxygenases-hydroxyhydroquinone 1,2-dioxygenase and chlorohydroxyhydroquinone 1,2-dioxygenase. The maleylacetate reductases produced during the growth on both substrates were identical in substrate specificity. The activity towards NADPH and maleylacetate was higher than towards NADH and chloromaleylacetate. The hydroxyhydroquinone dioxygenases were similar in stability, subunit weight molecular, and narrow substrate specificity. The oxidation rate of 6-chlorohydroxyhydroquinone by the hydroxyhydroquinone dioxygenases was about 10% of the oxidation rate of the unsubstituted hydroxyhydroquinone. The oxidation rate of 6-chlorohydroxyhydroquinone by the chlorohydroxyhydroquinone dioxygenase was 90% of the oxidation rate of the unsubstituted substrate.