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A three-component dicamba O-demethylase from Pseudomonas maltophilia, strain DI-6: Purification and characterization

2005; Elsevier BV; Volume: 437; Issue: 1 Linguagem: Inglês

10.1016/j.abb.2005.02.024

1096-0384

Sarbani Chakraborty, Mark Behrens, Patricia L. Herman, Alexander F. Arendsen, Wilfred R. Hagen, Deborah Carlson, Xiao-Zhuo Wang, Donald P. Weeks,

Microbial bioremediation and biosurfactants

Dicamba O-demethylase is a multicomponent enzyme that catalyzes the conversion of the herbicide 2-methoxy-3,6-dichlorobenzoic acid (dicamba) to 3,6-dichlorosalicylic acid (DCSA). The three components of the enzyme were purified and characterized. Oxygenase(DIC) is a homotrimer (alpha)3 with a subunit molecular mass of approximately 40 kDa. FerredoxinDIC and reductaseDIC are monomers with molecular weights of approximately 14 and 45 kDa, respectively. EPR spectroscopic analysis suggested the presence of a single [2Fe-2S](2+/1+) cluster in ferredoxinDIC and a single Rieske [2Fe-2S](2+; 1+) cluster within oxygenaseDIC. Consistent with the presence of a Rieske iron-sulfur cluster, oxygenaseDIC displayed a high reduction potential of E(m,7.0) = -21 mV whereas ferredoxinDIC exhibited a reduction potential of approximately E(m,7.0) = -171 mV. Optimal oxygenaseDIC activity in vitro depended on the addition of Fe2+. The identification of formaldehyde and DCSA as reaction products demonstrated that dicamba O-demethylase acts as a monooxygenase. Taken together, these data suggest that oxygenaseDIC is an important new member of the Rieske non-heme iron family of oxygenases.