Olivas E, deWaal D J, Wilkins R G
J Inorg Biochem. 1979 Nov;11(3):205-12. doi: 10.1016/s0162-0134(00)80018-5.
The reduction by dithionite ion (in excess) of methemerythrin-anion adducts, Hr+X-, to deoxyhemerythrin, Hr degree, has been examined at 25 degrees and pH 6.3 and 8.2. The results accord with the scheme: S2O42- in equilibrium 2SO2- rapid Hr+X- in equilibrium Hr++X- k-1, k1 Hr++SO2- leads to PRODUCT k2 with X- = Br-, HCO2-, CNO-, and F-, k2[SO2-] greater than k1[X-], and the pseudo first-order rate constant, kobs (= k-1), is independent of [X-] and [S2O42-]. Only with X- = NCS- is k2[SO2-] approximately k1[X-] and kobs = a[S2O42-]1/2 (b[NCS-] + [S2OR2-]1/2)-1. Values at pH 6.3 of k-1 (sec-1) and k1 (M-1 sec-1), obtained by anation and anion displacement reactions, are 2.3 x 10(-3), 1.6 x 10(-2) (Br-); 1.5 x 10(-3), 1.2 x 10(-2) (HCO2-); 1.3 x 10(-4), 0.52 (CNO-) and approximately 2 x 10(-4), 3.3 x 10(-3) (CN-, pH 7.0). Values of k-1 from reduction and displacement methods are in good agreement with each other. The value of k2 (1.6 x 10(5) M-1 sec-1, pH 6.3) in somewhat smaller than that for reduction of the met form of hemoproteins. There is only a small effect of pH on rates. Direct reduction of Hr+CN- does not occur, in contrast with Mb+CN-.
在25℃、pH值为6.3和8.2的条件下，研究了连二亚硫酸根离子（过量）将高铁红蛋白阴离子加合物Hr⁺X⁻还原为脱氧高铁红蛋白Hr°的过程。结果符合以下反应历程：S₂O₄²⁻⇌2SO₂⁻快速反应，Hr⁺X⁻⇌Hr⁺⁺X⁻（k⁻¹，k₁），Hr⁺⁺SO₂⁻→产物（k₂），其中X⁻ = Br⁻、HCO₂⁻、CNO⁻和F⁻，k₂[SO₂⁻]＞k₁[X⁻]，且准一级速率常数kobs（= k⁻¹）与[X⁻]和[S₂O₄²⁻]无关。仅当X⁻ = NCS⁻时，k₂[SO₂⁻]≈k₁[X⁻]，且kobs = a[S₂O₄²⁻]¹/²（b[NCS⁻] + [S₂OR₂⁻]¹/²）⁻¹。通过氨解和阴离子置换反应在pH 6.3时得到的k⁻¹（秒⁻¹）和k₁（M⁻¹秒⁻¹）的值分别为：2.3×10⁻³，1.6×10⁻²（Br⁻）；1.5×10⁻³，1.2×10⁻²（HCO₂⁻）；1.3×10⁻⁴，0.52（CNO⁻）和约2×10⁻⁴，3.3×10⁻³（CN⁻，pH 7.0）。还原法和置换法得到的k⁻¹值彼此吻合良好。k₂的值（pH 6.3时为1.6×10⁵ M⁻¹秒⁻¹）略小于血红蛋白高铁形式的还原值。pH值对反应速率的影响较小。与Mb⁺CN⁻不同，Hr⁺CN⁻不会直接发生还原反应。
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