Tenovuo J, Pruitt K M, Mansson-Rahemtulla B, Harrington P, Baldone D C
Biochim Biophys Acta. 1986 Apr 22;870(3):377-84. doi: 10.1016/0167-4838(86)90244-x.
The lactoperoxidase-catalyzed oxidation of thiocyanate (SCN-) was studied in the pH range 3-8. The ultraviolet spectra of the oxidation products, the hypothiocyanite ion, OSCN- (at pH 8) and hypothiocyanous acid, HOSCN (at pH 3), were recorded. The absorbance maxima for OSCN- and HOSCN were observed at 220 and 240 nm, respectively. The extinction coefficients for OSCN- and HOSCN were determined to be 3870 (at 220 nM) and 95 M-1 X cm-1 (at 240 nM), respectively. Pure solutions of OSCN- (at pH 8) and HOSCN (at pH 3) were stable, but the mixtures of these two species at intermediate pH values were unstable. The decomposition could be divided into two periods, an initial period of rapid increase in oxidizing equivalents and a second period of decomposition. Decomposition during the second period followed first-order kinetics, and the pH-dependence of the apparent first-order rate constant was consistent with a decomposition mechanism which involved HOSCN. The first-order rate constant for this step was estimated to be 6 X 10(-3) s-1 at 37 degrees C.
在pH值3至8的范围内研究了乳过氧化物酶催化的硫氰酸盐（SCN-）氧化反应。记录了氧化产物次硫氰酸根离子OSCN-（在pH 8时）和次硫氰酸HOSCN（在pH 3时）的紫外光谱。观察到OSCN-和HOSCN的最大吸收波长分别为220和240 nm。确定OSCN-和HOSCN的消光系数分别为3870（在220 nM时）和95 M-1×cm-1（在240 nM时）。OSCN-（在pH 8时）和HOSCN（在pH 3时）的纯溶液是稳定的，但这两种物质在中间pH值下的混合物是不稳定的。分解可分为两个阶段，第一阶段是氧化当量迅速增加，第二阶段是分解。第二阶段的分解遵循一级动力学，表观一级速率常数的pH依赖性与涉及HOSCN的分解机制一致。在37℃时，该步骤的一级速率常数估计为6×10（-3）s-1。
