Transketolase is an enzyme of each the pentose phosphate pathway in all organisms and the Calvin cycle of photosynthesis. Transketolase is a important enzyme in the non-oxidative branch of the pentose phosphate pathway that transfers a two-carbon glycoaldehyde unit from ketose-donor to aldose-acceptor sugars. Transketolase is also involved in the photosynthetic Calvin cycle in plants and autotrophic germs. Thiamine diphosphate and calcium are crucial cofactors in Transketolase catalyzed reactions. In mammals, transketolase connects the pentose phosphate pathway to glycolysis, feeding excess sugar phosphates into the main carbohydrate metabolic pathways. Its existence is needed for the manufacturing of NADPH, specially in tissues actively engaged in biosyntheses, these as fatty acid synthesis by the liver and mammary glands, and for steroid synthesis by the liver and adrenal glands.