Purification and Characterization of NADPH-Dependent Cr(Ⅵ) Reductase from Escherichia coli ATCC 33456

A soluble Cr(Ⅵ) reductase was purified from the cytoplasm of Escherichia coli ATCC 33456. The molecular mass was estimated to be 84 and 42 kDa by gel filtration and SDS-polyacrylamide gel electrophoresis, respectively, indicating a dimeric structure. The pI was 4.66, and optimal enzyme activity was obtained at pH 6.5 and 37℃. The most stable condition existed at pH 7.0. The purified enzyme used both NADPH and NADH as electron donors for Cr(Ⅵ) reduction, while NADPH was the better, conferring 61% higher activity than NADH.