Add time:07/28/2019         Source:sciencedirect.com

Cell-free extracts of Alcaligenes sp. CKCr-6A that was isolated from Sabzevar of Iran catalyzes the NADH-dependent reduction of selenate and selenite to elemental selenium. Selenate reductase enzyme was purified with following purification process involved (NH4)2SO4 precipitation, followed by using Q-Sepharose and phenyl-Sepharose chromatography. Using gel filtration, the relative molecular mass of the enzyme was measured to be 197 kDa. The outcomes showed that selenate reductase exists as a tetramer with molecular masses 70 kDa, 45 kDa, 35 kDa and 27 kDa. The Vmax and Km values of selenate reductase were 3.96 μmol min− 1 mg− 1 of protein and 1.8 mM, respectively. The Vmax and Km were detected 1.26 μmol min− 1 mg− 1 of protein and 5.47 mM towards selenite as a substrate, respectively. The enzyme revealed its optimum activity at pH 6 and 35 °C. Divalent cations, such as Ca2 + and Mg2 +, had no effect on the activity, while similar concentrations of Pb2 + and Cu2 + and some Metabolic poisons such as N-ethyl maleimide eliminated the activity. In addition analysis discovered the role of Mo+ 2 in selenate reductase. Results showed that [EMIm][Br] have a positive effect on activity and thermal stability of the reductase and also is effective on the amount and size of synthesized Se-NPs that mediated by this enzyme.

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