title: Purification and characterization of a secreted recombinant phosphotriesterase (parathion hydrolase) from Streptomyces lividans.
abstract: A heterologous phosphotriesterase (parathion hydrolase), previously cloned from a Flavobacterium species into Streptomyces lividans, was secreted at high levels and purified to homogeneity. N-terminal analysis revealed that it had been processed in the same manner as the native membrane-bound Flavobacterium hydrolase. The enzyme consisted of a single polypeptide with an apparent molecular weight of 35,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Substrate specificity studies showed Kms of 68 microM for parathion, 46 microM for O-ethyl O-p-nitrophenyl phenylphosphonothioate, 599 microM for methyl parathion, and 357 microM for p-nitrophenyl ethyl(phenyl)phosphinate. Temperature and pH optima were 45 degrees C and 9.0, respectively. The purified enzyme was inhibited by 1 mM dithiothreitol and 1 mM CuSO4. After chelation and inactivation by o-phenanthroline, however, activity could be partially restored by 1 mM CuCl or 1 mM CuSO4. The results showed that the purified recombinant parathion hydrolase has the same characteristics as the native Flavobacterium hydrolase. This system provides a source of milligram quantities of parathion hydrolase for future structural and mechanism studies and has the potential to be used in toxic waste treatment strategies.
authors.affiliation: Department of Biomedicinal Chemistry, School of Pharmacy, University of Maryland, Baltimore 21201.
authors.forename: S S
authors.initials: SS
authors.lastname: Rowland
authors.forename: M K
authors.initials: MK
authors.lastname: Speedie
authors.forename: B M
authors.initials: BM
authors.lastname: Pogell
mesh_terms: D000595:Amino Acid Sequence; D043303:Aryldialkylphosphatase; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D013302:Streptomyces / Q000201:enzymology* / Q000235:genetics; D013379:Substrate Specificity
chemical_list: D011994:Recombinant Proteins; D010744:Phosphoric Monoester Hydrolases; D043303:Aryldialkylphosphatase