来自多毛纲动物索氏阔沙蚕牵缩肌的肌红蛋白的一些氧化还原特性。

Some redox properties of myohemerythrin from retractor muscle of Themiste zostericola.

作者信息

Harrington P C, Muhoberac B B, Wharton D C, Wilkins R G

出版信息

Biochemistry. 1981 Oct 13;20(21):6134-9. doi: 10.1021/bi00524a034.

Abstract

Distinct semimetmyohemerythrin species are produced by one-electron oxidation of deoxymyohemerythrin and one-electron reduction of metmyohemerythrin. The former, (semimetmyo)o, changes (greater than or equal to 90%) to the latter, (semimetmyo)R, with k = 1.0 x 10(-2) s-1, delta H = 15.1 kcal mol-1 and delta S = -17 eu. Oxidation of (semimetmyo)o by Fe(CN)6(3)- rapidly produces an unstable metmyohemerythrin form which converts to the final metmyohemerythrin with k = 4.6 x 10(-3) s-1, delta H = 16.8 kcal mol-1, and delta S = -13 eu. The two met forms react at the same rate with N3-, but the unstable form reacts very rapidly with S2O4(2-) in contrast to stable metmyohemerythrin. (Semimetmyo)R or a mixture of metmyohemerythrin and deoxymyohemerythrin equilibrate very slowly to a mixture containing all three species. The rate constants for disproportionation and comproportionation are 0.89 M-1 s-1 and 9.4 M-1 s-1, respectively. EPR spectra near liquid He temperatures and optical absorption spectra have been used to characterize and measure the rates at 25 degrees C, pH 8.2, and I = 0.15 M. The comparative behavior of octameric and monomeric protein is discussed.

摘要

脱氧肌红血球素的单电子氧化和高铁肌红血球素的单电子还原会产生不同的半肌红血球素物种。前者，即（半肌红血球素）o，以k = 1.0×10⁻² s⁻¹、ΔH = 15.1 kcal mol⁻¹和ΔS = -17 eu的速率转变（≥90%）为后者，即（半肌红血球素）R。Fe(CN)₆³⁻对（半肌红血球素）o的氧化会迅速产生一种不稳定的高铁肌红血球素形式，该形式会以k = 4.6×10⁻³ s⁻¹、ΔH = 16.8 kcal mol⁻¹和ΔS = -13 eu的速率转变为最终的高铁肌红血球素。两种高铁形式与N₃⁻反应速率相同，但与稳定的高铁肌红血球素相比，不稳定形式与S₂O₄²⁻反应非常迅速。（半肌红血球素）R或高铁肌红血球素与脱氧肌红血球素的混合物非常缓慢地达到包含所有三种物种的混合物的平衡。歧化和逆歧化的速率常数分别为0.89 M⁻¹ s⁻¹和9.4 M⁻¹ s⁻¹。在液氦温度附近的EPR光谱和光吸收光谱已用于在25℃、pH 8.2和I = 0.15 M条件下表征和测量反应速率。讨论了八聚体和单体蛋白的比较行为。