Induction of carbofuran oxidation to 4-hydroxycarbofuran by Pseudomonas sp. 50432

Pseudomonas sp. 50432 biotransformed a highly toxic pesticide, carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) to 7-phenol (2,3-dihydro-2,2-dimethyl-7-hydroxy benzofuran) and several unknown metabolites. One of the unknown metabolites identified by gas chromatography/mass spectroscopy was 4-hydroxycarbofuran (2,3-dihydro-2,2-dimethyl-4-hydroxybenzofuran-7-yl methylcarbamate). It had a mass (237) similar to 3-hydroxycarbofuran and 5-hydroxycarbofuran but different fragmentation patterns. This is the first report in which an inducible oxidative enzyme, hydroxylase, mediated the conversion of carbofuran to 4-hydroxycarbofuran. A second constitutively synthesized enzyme hyrolase transformed carbofuran to 7-phenol.

Purification and biochemical characterization of the carbamate hydrolase from Pseudomonas sp. 50432

A soluble carbamate hydrolase that had a wide specificity was purified 2032-fold from Pseudomonas sp. 50432. This was achieved using a combination of anion-exchange, gel-filtration and hydrophobic-interaction- chromatography techniques. Carbamate hydrolase cleaved the ester linkage of the N-methylcarbamates. The native enzyme was a monomer with a molecular mass of 88 kDa. The optimum pH and temperature of the enzyme activity were 8.5 and 37 degrees C respectively. The tested cations or EDTA did not affect the enzyme activity. However, 2-mercaptoethanol reversibly inhibited the enzyme activity. The enzyme showed the K(m) values of 16 and 12 microM for carbofuran and carbaryl respectively. The purified enzyme did not hydrolyse o-nitrophenyl dimethylcarbamate but hydrolysed several N-methylcarbamates and 1-naphthyl acetate.