The reversible reduction of horse metmyoglobin by the iron(II) complex of trans-1,2-diaminocyclohexane-N,N,N,n-tetraacetate.
The reduction of metmyoglobin by the iron(II) complex of trans-1,2-diaminocyclohexane-N,N,N'N'-tetraacetate (FeCDTA2-) has been investigated. The equilibrium constant, measured spectrophotometrically, is 0.21 with a resulting reduction potential of 0.050 V for Mb0. The rate constant for the reduction is 28 M-1 sec-1 with a deltaH ++ of 13 kcal M-1 and deltaS ++ of -11 eu. Both CN- and OH- inhibit the reduction because of the relatively low reactivity of cyanometmyoglobin (Mb+CN-) and ionized metmyglobin (Mb+OH-). The rate constant for the reduction of Mb+CN- by FeCDTA2- is 4.0 X 10(-2) M-1 sec-1 and that for reduction of Mb+OH- is 4.8 M-1 sec-1. The nitric oxide complex of metmyoglobin is reduced with a rate constant of 10 M-1 sec-1. The kinetics of oxidation of oxymyoglobin by FeCDTA- were studied. The data are consistent with a mechanism where oxidation takes place entirely through the deoxy form. A rate constant of 1.45 X 10(2) M-1 sec-1 was calculated for the oxidation of deoxymyoglobin by FeCDTA-, in equilibrium constant and rate constant for reduction. The above data are discussed in terms of a simple outer-sphere reduction reaction.
D000085:Acetates; D000818:Animals; D002614:Chelating Agents; D003486:Cyanides; D003514:Cyclohexylamines; D004492:Edetic Acid / Q000031:analogs & derivatives; D005296:Ferrous Compounds; D006736:Horses; D006863:Hydrogen-Ion Concentration; D007501:Iron; D007700:Kinetics; D009211:Myoglobin; D009569:Nitric Oxide; D010084:Oxidation-Reduction; D010100:Oxygen; D011485:Protein Binding
D000085:Acetates; D002614:Chelating Agents; D003486:Cyanides; D003514:Cyclohexylamines; D005296:Ferrous Compounds; D009211:Myoglobin; D009569:Nitric Oxide; C005390:CDTA; D004492:Edetic Acid; D007501:Iron; D010100:Oxygen