Abstract
Thiazolealanine (α-amino-β-(4-methylthiazole-5-yl) propionic acid) was effective one thousandth as low as thiazole moiety of thiamine for growth of E.coli W, Th-less strain, and also it was effective only one ten thousandth as low as thiazole for reversion of L-phenylalanine action by which derepression of the thiamine biosynthesizing enzymes was brought in E.coli K_<12>. Enzymatic conversion of thiazolealanine to thiazole was demonstrated by incubation of a crude extract of E.coli with thiazolealanine, coupling with thiamine synthesizing system from OMP-pyrophosphate although only 0.01% of the substrate was converted to thiazole. From the results obtained, it was concluded that thiazolealanine as a direct precursor of thiazole might probably be excluded in E.coli.
