Gene cloning and properties of a methyl parathion hydrolase from Pseudomonas sp.1-7

In order to isolate organophosphorus hydrolases and their encoding genes,a bacterium with the capability of degrading methyl parathion,identified as Pseudomonas sp. by 16S rDNA analysis,was isolated from active sludge in organophosphate-treated aeration basin,and designated as Pseudomonas sp. 1-7. The full-length of methyl parathion hydrolase (MPH) gene, ophc3, from this bacterium was cloned by constructing genomic library.The ophc3 gene is 975 bp long, encoding a polypeptide of 324 amino acids that includes a signal peptide of 24 aa. The gene ophc3 was expressed in E.coli. The recombinant methyl parathion hydrolase OPHC3 was purified,and the enzymatic properties were studied. The optimum temperature and pH for enzyme activity are 45 ℃ and pH 8.0,respectively.It also shows good pH stability and poor temperature stability.Over 70% of the relative activities were retained from pH 6.0-10.0.About 46.77% of the activity was retained after heating the enzyme at 60 ℃ for 10 min.