TAILIEUCHUNG - Báo cáo khoa học: Ferrocyanide ) a novel catalyst for oxymyoglobin oxidation by molecular oxygen

A comparative study of the rates of ferrocyanide-catalyzed oxidation of several oxymyoglobins by molecular oxygen is reported. Oxidation of the native oxymyoglobins from sperm whale, horse and pig, as well as the chemically modified (MbO2) sperm whale oxymyoglobin, with all accessible His residues alkylated by sodium bromoacetate (CM-MbO2), and the mutant sperm whale oxymyoglobin [MbO2(His119 fiAsp)], was studied. | ễFEBS Journal Ferrocyanide - a novel catalyst for oxymyoglobin oxidation by molecular oxygen G. B. Postnikova S. A. Moiseeva E. A. Shekhovtsova E. V. Goraev and V. S. Sivozhelezov Institute of CellBiophysics Russian Academy of Sciences Pushchino Russia Keywords catalysis ferrocyanide modification myoglobin oxidation Correspondence G. B. Postnikova or V. S. Sivozhelezov Institute of Cell Biophysics Russian Academy of Sciences Pushchino Moscow Region 142290 Russia Fax 7 4967 330509 Tel 7 4967 739155 E-mail gbpost@ gb_post@ vsivo@ Received 13 March 2007 revised 4 June 2007 accepted 22 August 2007 doi A comparative study of the rates of ferrocyanide-catalyzed oxidation of several oxymyoglobins by molecular oxygen is reported. Oxidation of the native oxymyoglobins from sperm whale horse and pig as well as the chemically modified MbO2 sperm whale oxymyoglobin with all accessible His residues alkylated by sodium bromoacetate CM-MbO2 and the mutant sperm whale oxymyoglobin MbO2 His119 fi Asp was studied. The effect of pH ionic strength and the concentration of anionic catalyst ferrocyanide Fe CN 6 4- on the oxidation rate is investigated as well as the effect of MbO2 complexing with redox-inactive Zn2 which forms the stable chelate complex with functional groups of His119 Lys16 and Asp122 all located nearby. The catalytic mechanism was demonstrated to involve specific Fe CN 6 4- binding to the protein in the His119 region which agrees with a high local positive electrostatic potential and the presence of a cavity large enough to accommodate Fe CN 6 4- in that region. The protonation of the nearby His113 and especially His116 plays a very important role in the catalysis accelerating the oxidation rate of bound Fe CN 6 4- by dissolved oxygen. The simultaneous occurrence of both these factors . specific binding of Fe CN 6 4- to the protein and its fast reoxidation by oxygen is necessary for the efficient .

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