Kinetics of bisulphite cleavage of the three biological phosphorylated derivatives of thiamine.

Bisulphite/sulphite cleaves thiamine and its biological phosphorylated derivatives into the same pyrimidine moiety and their respective thiazole moiety with pseudo-first order kinetic constants following the order of thiamine greater than thiamine monophosphate greater than thiamine diphosphate greater than thiamine triphosphate over the pH range of 3.9 to 7.0. The activation energy was 14.8 kcal/mol for all four thiamines at pH 5.2 and over the temperature range of 25 to 65 degrees C. The rate differences may be rationalized in terms of differences in the pH-dependent electronic, charge and conformation distributions of the various thiamine species.