Purification and Properties of Pendimethalin Nitroreductase from Bacillus circulans

摘要

A pendimethalin nitroreductase was purified from Bacillus circulans to 52-fold increase with a recovery of 21.1% and had a specific activity of 4.16 U/mg. The molecular weight was 27 kDa. The optimum pH and temperature were 7.5 and 35 degrees C, respectively. Fe2+, Ca2+, Mg2+ and Mn2+ did not cause any effect on the enzyme activity, whereas Ag+, Hg2+ significantly inhibited it. The pendimethalin nitroreductase from B. circulans required NADPH as cofactor. It was not affected by GSH, DTT, L-Cys and beta-mercaptoethanol but inhibited by p-hydroxymercuribenzoate, N-ethylmaleimide, and iodoacetamide. EDTA, 1,10-phenanthroline and alpha,alpha'-dipyridyl had a moderate effect on the enzyme activity. The nitroreductase reduced all the tested nitroaromatic compounds but was more active towards pendimethalin and trifluralin. The K-M and V-max for the enzyme reaction using pendimethalin as a substrate were 4.35 mu M and 620 mu moles mg(-1) min(-1), respectively. The broad substrate specificity towards dinitroaniline herbicides suggested the enzyme to be used as a potent reducing agent of these toxic compounds. This is the first report for the purification and characterization of pendimethalin nitroreductase from any bacterial or fungal species.