Abstract
Thiamine decomposition reaction, catalized by the bacterial thiaminase I in the system containing pyridoxine as a second substrate was investigated. The transfer of the pyrimidine group from thiamine to nitrogen atom in pyridoxine was shown by isolating the reaction product and by determining its chemical structure. On the basis of wave length shifts with pH of the ultraviolet light absorption peaks caused by an electron-donating substitution, it was concluded that the product ionized in the phenolic hydroxyl group to give the dipolar ionic form, N-(4-amino-2-methyl-5-pyrimidinyl)-methyl pyridoxinium-3-phenolate, in neutral or alkaline solutions but took the cationic form in acidic solution. Chlorine was not detected from crystals of the product. These results suggest that the crystalline product is a betain-like inner salt. Two kinds of crystal forms, plates and needles, were observed, and the melting point of crystals (plates) was 204.5〜206.0℃ (decomp.). The NMR and IR spectra of pyrimidinyl pyridoxinium-3-phenolate were also presented.
