Leichter J, Joslyn M A
Biochem J. 1969 Jul;113(4):611-5. doi: 10.1042/bj1130611.
Results are presented on the rate of thiamin cleavage by sulphite in aqueous solutions as affected by temperature (20-70 degrees ), pH(2.5-7.0), and variation of the concentration of either thiamin (1-20mum) or sulphite (10-5000mum as sulphur dioxide). Plots of the logarithm of percentage of residual thiamin against time were found to be linear and cleavage thus was first-order with respect to thiamin. At pH5 the rate was also found to be proportional to the sulphite concentration. In the pH region 2.5-7.0 at 25 degrees the rate constant was 50m(-1)hr.(-1) at pH5.5-6.0, and decreased at higher or lower pH values. The rate of reaction increased between 20 degrees and 70 degrees , indicating a heat of activation of 13.6kcal./mole.
本文给出了亚硫酸盐在水溶液中对硫胺素的裂解速率，该速率受温度（20 - 70摄氏度）、pH值（2.5 - 7.0）以及硫胺素浓度（1 - 20μM）或亚硫酸盐浓度（以二氧化硫计为10 - 5000μM）变化的影响。结果发现，残留硫胺素百分比的对数与时间的关系图呈线性，因此硫胺素的裂解反应对硫胺素而言是一级反应。在pH5时，反应速率也与亚硫酸盐浓度成正比。在25摄氏度下，pH值范围为2.5 - 7.0时，pH5.5 - 6.0时的反应速率常数为50M⁻¹hr⁻¹，在更高或更低的pH值时该常数降低。反应速率在20摄氏度至70摄氏度之间增加，表明活化热为13.6千卡/摩尔。
