Cytosolic thiamin pyrophosphokinase (TPK1) catalyzes the reaction of thiamin (THMN) and ATP to form thiamin diphosphate (ThDP aka thiamin pyrophosphate) and ADP. ThDP is an active cofactor for transketolase, pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, enzymes involved in glycolysis and energy production. The gene encoding the human enzyme has been cloned and its protein product has been shown to have TPK1 activity (Nosaka et al. 2001; Zhao et al. 2001). Its homodomeric structure and association with Mg2+ are inferred from properties of the homologous yeast enzyme (Baker et al. 2001).