Thiamine pyrophosphokinase (TPK; EC 2.7.6.2) is a cellular enzyme involved in the regulation of thiamine metabolism. TPK catalyzes the conversion of thiamine, a form of vitamin B1, to thiamine pyrophosphate (TDP, or TPP). TDP is an active cofactor for enzymes involved in glycolysis and energy production, including transketolase, pyruvate dehydrogenase, and alpha-ketoglutarate dehydrogenase.By EST database searching with the S. pombe TPK gene (tnr3), Nosaka et al. (1999) identified the mouse Tpk1 gene. Using mouse Tpk1 to screen a human liver cDNA library, Nosaka et al. (2001) identified the human counterpart, TPK1, which was independently cloned by Zhao et al. (2001). Both groups found that TPK1 encodes a deduced 243-amino acid protein that shares 89% sequence identity with the mouse Tpk1 protein.