tailieunhanh - Báo cáo Y học: Bromoperoxidase activity of vanadate-substituted acid phosphatases from Shigella flexneri and Salmonella enterica ser. typhimurium

Vanadium haloperoxidases and the bacterial class A nonspecific acid phosphatases have a conserved active site. It is shown that vanadate-substituted recombinant acid phosphatase from Shigella flexneri (PhoN-Sf) and Salmonella enterica ser. typhimurium (PhoN-Se) in the presence of H2O2 are able to oxidize bromide to hypobromous acid. Vanadate is essential for this activity. The kinetic parameters for the artificial bromoperoxidases have been determined. The Km value for H2O2 is about the same as that for the vanadium bromoperoxidases from the seaweed Ascophyllum nodosum. . | Eur. J. Biochem. 269 2162-2167 2002 FEBS 2002 doi j Bromoperoxidase activity of vanadate-substituted acid phosphatases from Shigella flexneri and Salmonella enterica ser. typhimurium Naoko Tanaka1 Valerie Dumay1 Qianning Liao2 Alex J. Lange2 and Ron Wever1 1Institute for Molecular Chemistry University of Amsterdam The Netherlands department of Biochemistry Molecular Biology and Biophysics University of Minnesota Medical School and College of Biological Sciences Minneapolis Minnesota USA Vanadium haloperoxidases and the bacterial class A nonspecific acid phosphatases have a conserved active site. It is shown that vanadate-substituted recombinant acid phosphatase from Shigella flexneri PhoN-Sf and Salmonella enterica ser. typhimurium PhoN-Se in the presence of H2O2 are able to oxidize bromide to hypobromous acid. Vanadate is essential for this activity. The kinetic parameters for the artificial bromoperoxidases have been determined. The Km value for H2O2 is about the same as that for the vanadium bromoperoxidases from the seaweed Ascophyllum nodosum. However the Km value for Br- is about 10-20 times higher and the turnover values of about min-1 and 33 min-1 for PhoN-Sf and PhoN-Se respectively are much slower than those of the native bromoperoxidase. Thus despite the striking similarity in the active-site structures of the vanadium haloperoxidases and the acid phophatase the turnover frequency is low and clearly the active site of acid phosphatases is not optimized for haloperoxidase activity. Like the native vanadium bromoperoxidase the vanadate-sub-stituted PhoN-Sf and PhoN-Se catalyse the enantioselective sulfoxidation of thioanisole. Keywords acid phosphatase brominating activity enantio-selective sulfoxidation vanadium bromoperoxidase vanadium chloroperoxidase. Vanadium haloperoxidases are enzymes that catalyse the oxidation of a halide by hydrogen peroxide to the corresponding hypohalous acids according to H2O2 H X- H2O HOX .