Thiamine monophosphate synthase (TMP) (EC:2.5.1.3) catalyses the substitution of the pyrophosphate of 2-methyl-4-amino-5- hydroxymethylpyrimidine pyrophosphate by 4-methyl-5- (beta-hydroxyethyl)thiazole phosphate to yield thiamine phosphate [1]. This Pfam family also includes the regulatory protein TENI (Swiss:P25053), a protein from Bacillus subtilis that regulates the production of several extracellular enzymes by reducing alkaline protease production [2]. While TenI shows high sequence similarity with thiamin phosphate synthase, the purified protein has no thiamin phosphate synthase activity. Instead, it is a thiazole tautomerase [3].

1: Characterization of the Bacillus subtilis thiC operon involved in thiamine biosynthesis. Zhang Y, Taylor SV, Chiu HJ, Begley TP; J Bacteriol 1997;179:3030-3035. PMID:9139923

2: Cloning and characterization of a pair of novel genes that regulate production of extracellular enzymes in Bacillus subtilis. Pang AS, Nathoo S, Wong SL; J Bacteriol 1991;173:46-54. PMID:1898926

3: A missing enzyme in thiamin thiazole biosynthesis: identification of TenI as a thiazole tautomerase. Hazra AB, Han Y, Chatterjee A, Zhang Y, Lai RY, Ealick SE, Begley TP; J Am Chem Soc. 2011;133:9311-9319. PMID:21534620