The Action of Bacterial Thiaminase I on Thiamine:II. A Decomposition Product of Thiamine, Pyrimidinyl-Nicotinic Acid

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The activation of thiaminase I with various substances was investigated. It was observed that the purified bacterial thiaminase I, which was separated from some activators, and crude shell-fish thiaminase I could be activated with nicotinic acid. It was recognized that some basic amino acids and some others activate the enzyme reaction, although, in some cases, the rate of the activation is not significant.Pyrimidinyl-nicotinic acid (Pm-NiA) in the reaction mixture of thiamine, nicotinic acid, and bacterial thiaminase I was detected by paper chromatography. To determine the amount of Pm-NiA produced in the reaction, a chemical assay of Pm-NiA was developed. Using this method, the best conditions for the enzyme reaction were established.Pm-NiA was isolated by column chromatography using Amberite CG-50, as a decomposition product of thiamine by the purified bacterial thiaminase in the presence of nicotinic acid. The yield of Pm-NiA was about 71% of the amount formed in the reaction mixture as estimated by the chemical assay. The isolated crystals showed mp 233° and Rf 0.39 (n-butanol:methanol:water, 2:1:1). Ultraviolet absorption maximum was at 245mμ (pH 2), and 230 and 270mμ (pH 9), in agreement with those of chemically synthesized Pm-NiA.
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