The reversible reduction of horse metmyoglobin by the iron(II) complex of trans-1,2-diaminocyclohexane-N,N,N,n-tetraacetate

J C CassattJ W Bender


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.


Apr 30, 1987·Biochimica Et Biophysica Acta·K HegetschweilerP E Wright
Apr 1, 1977·CRC Critical Reviews in Food Science and Nutrition·G G Giddings
Sep 30, 1983·Biochimica Et Biophysica Acta·R J Balahura, R G Wilkins
Jul 6, 1992·Biochimica Et Biophysica Acta·C BrunelGérard Simonneaux
Jan 15, 1979·Biochemical and Biophysical Research Communications·A G Mauk, H B Gray
Jun 6, 1977·Biochemical and Biophysical Research Communications·T R LeBon, J C Cassatt
Jul 10, 2019·JAMA Pediatrics·Lorraine I Kelley-QuonAdam M Leventhal
Jun 9, 2005·Chemical Reviews·Gérard Simonneaux, Arnaud Bondon

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