What vitamin serves as a cofactor for oxidative decarboxylation and transketolase?

Thiamine, also known as vitamin B1, plays a crucial role as a cofactor in multiple enzymatic reactions, particularly in carbohydrate metabolism. Two key processes that depend on thiamine are oxidative decarboxylation and transketolase activity.

In oxidative decarboxylation, thiamine is essential for the proper function of the pyruvate dehydrogenase complex, which converts pyruvate into acetyl-CoA, a critical substrate for the Krebs cycle. This reaction is vital for energy production as it helps to link glycolysis to the TCA cycle, thereby facilitating the metabolism of carbohydrates and fats.

Transketolase, on the other hand, is part of the pentose phosphate pathway (PPP), which is important for generating NADPH (used in reductive biosynthesis) and ribose-5-phosphate (used for nucleotide synthesis). Thiamine serves as a coenzyme for transketolase, helping to transfer carbon units between sugars during the pathway.

The other vitamins listed do not fulfill these specific roles in oxidative decarboxylation or transketolase reactions. Vitamin A is primarily involved in vision and cellular differentiation, riboflavin (B2) functions as a