Effect of Amino Acids and Purine Bases on Thiamine Synthesis by Escherichia coli

Abstract

Phenylalanine and histidine, out of several amino acids tested by the addition to the growth medium of Escherichia coli, showed stimulatory effects on thiamine production y the cells. In order to know the mechanism of phenylalanine action, it was compared with the adenine effect in which adenine added to the growth medium caused a decrease in thiamine production of E. coli accom panying with the increase of thiamine synthesizing activity from hydroxymethylpyrimidine and thiazole. Phenylalanine had also a similar elevating effect on thiamine synthesizing activity from hy droxymethylpyrimidine and thiazole in spite of the increase in cel lular thiamine contents. The phenylalanine effect could be abolished by a simultaneous thiazole addition at a physiological concentra tion for the organism in contrast with the adenine effect, which was arrested by hydroxymethylpyrimidine addition. The phenyl alanine effect is supposed to be concerned with the synthesis of thiazole moiety of thiamine. The regulation of thiamine biosyn thesis in E. coli was also discussed.

Inhibition by Phenylalanine of Thiazole Biosynthesis in Escherichia coli

“…We thank Takashi Kawasaki, Hiroshima University, for kindly supplying Escherichia coli PT-Ri. and adenine (9,12,14). However, very little is known yet about the biosynthetic pathway of the thiazole moiety of thiamine in microorganisms.…”

“…During an investigation into the control of thiamine biosynthesis in E. coli, we found that phenylalanine caused derepression of thiamine biosynthetic enzymes accompanied by an increase in the level of cellular thiamine (9,10). Although the precise mechanism for the effect of this amino acid on thiamine biosynthesis remains to be clarified, it was thought that phenylalanine might compete with thiazole in the regulation of thiamine biosynthesis since thiazole, at growth factor levels, abolished the phenylalanine-enhanced activities of these enzymes.…”