Catalyzes the phosphorylation of thiamine to thiamine pyrophosphate (TPP) (PubMed:17611796). TPP is an active cofactor for enzymes involved in glycolysis and energy production (PubMed:17611796). Plant leaves require high levels of TPP for photosynthesis and carbohydrate metabolism (PubMed:17611796). ATP + thiamine = AMP + H(+) + thiamine diphosphate Optimum pH is 7. Active between pH 6 and pH 8. Optimum temperature is 37 degrees Celsius. Cofactor biosynthesis; thiamine diphosphate biosynthesis; thiamine diphosphate from thiamine: step 1/1. Expressed in roots, leaves and flowers. No visible phenotype under normal growth conditions (PubMed:17611796). Tpk1 and tpk2 double mutants exhibit a seedling lethal phenotype (PubMed:17611796). Belongs to the thiamine pyrophosphokinase family.