Transketolase in the hexose monophosphate (HMP) pathway is dependent on which vitamin?

Transketolase is an enzyme that plays a critical role in the hexose monophosphate (HMP) pathway, which is also known as the pentose phosphate pathway. This enzyme is involved in the transfer of two-carbon units from one sugar to another, facilitating the conversion of various carbohydrates. Importantly, transketolase requires thiamine (vitamin B1) as a cofactor for its enzymatic activity.

Thiamine is essential for several enzymes that participate in carbohydrate metabolism, particularly in the decarboxylation processes and in the transketolase reaction. A deficiency in thiamine can lead to impaired function of transketolase, which can have significant metabolic consequences, as the HMP pathway is crucial for generating NADPH for biosynthetic reactions and ribose-5-phosphate for nucleotide synthesis.

In contrast, the other vitamins listed do not play a direct role in the function of transketolase. Vitamin B12 is primarily involved in the metabolism of amino acids and fatty acids, riboflavin (vitamin B2) is a precursor for flavin coenzymes involved in various redox reactions, and pyridoxine (vitamin B6) is essential for amino acid