Purification and characterization of maleylacetate reductase from Nocardioides simplex 3E utilizing phenoxyalcanoic herbicides 2,4-D and 2,4,5-T.

Maleylacetate reductase was isolated and purified from the Gram-positive strain Nocardioides simplex 3E which is able to utilize the phenoxyalcanoic herbicides 2,4-D and 2,4,5-T. Cells were grown on 2,4-D as the sole carbon source. The enzyme was purified by 380-fold with 3.0% yield. The purified maleylacetate reductase is a homodimer with subunit molecular mass of 37 kD. The enzyme required NADH as a cofactor; the Km for maleylacetate is 25 microM; Vmax (with NADH as cofactor) and kcat are 185 U/mg and 6845 min-1, respectively. The enzyme is very unstable; its pH and temperature optima are at 7.0-7.1 and 50 degrees C, respectively.