Catalyzes the irreversible aromatization of 2-((2R,5Z)-2-carboxy-4-methylthiazol-5(2H)-ylidene)ethyl phosphate (cThz*-P) to 2-(2-carboxy-4-methylthiazol-5-yl)ethyl phosphate (cThz-P), a step in the biosynthesis of the thiazole phosphate moiety of thiamine. Cannot use cThz* as substrate, indicating that the phosphate group is essential. Has no thiamine phosphate synthase activity, despite a high sequence similarity with ThiE. 2-[(2R,5Z)-2-carboxy-4-methylthiazol-5(2H)-ylidene]ethyl phosphate = 2-(2-carboxy-4-methylthiazol-5-yl)ethyl phosphate Cofactor biosynthesis; thiamine diphosphate biosynthesis. Homodimer. Strongly repressed by thiamine. Inactivation of this gene causes a delay in sporulation, but does not affect cell growth and the production of extracellular enzymes. Belongs to the thiazole tautomerase family. Was originally described as a regulatory protein involved in the regulation of the production of extracellular enzymes.