Transketolase （TK）, a thiamine diphosphate （ThDP）-dependent enzyme, catalyzes several key reactions of nonoxidative branch of pentose phosphate pathway. TK is a homodimer with two active sites that locate at the interface between the contacting monomers. Both ThDP and bivalent cations are strictly needed for TK activation, just like that for all ThDPdependent enzymes. TK exists in all organisms that have been investigated. Up to now, one TK gene （TKT） and two transketolase-like genes （TKTL1 and TKTL2） have been identified in human genome. TKTL1 is reported to play a pivotal role in carcinogenesis and may have important implications in the nutrition and future treatment of patients with cancer. Research- ers have found TK variants and reduced activities of TK enzyme in patients with neurodegenerative diseases, diabetes, and cancer. Recent studies indicated TK as a novel role in the prevention and therapy of these diseases.
