Facilitates the conversion of hydroxymethylpyrimidine phosphate to 4-amino-5-hydroxymethyl-2-methylpyrimidine-pyrophosphate.
Facilitates the combination of 4-amino-5-hydroxymethyl-2-methylpyrimidine-pyrophosphate and 4-methyl-5-(beta-hydroxyethyl)thiazole phosphate to form thiamine-phosphate.