Which coenzyme is essential for carboxylation reactions?

Carboxylation reactions are biochemical processes in which a carbon atom is added to a substrate, often as part of the synthesis of various metabolic intermediates. These reactions are crucial for the functioning of several metabolic pathways, including gluconeogenesis and fatty acid synthesis.

Biotin, also known as vitamin B7, serves as a key coenzyme for enzymes called carboxylases, which catalyze these carboxylation reactions. It is covalently bound to the enzyme through a lysine residue and plays a vital role in transferring carbon dioxide to substrates, facilitating the conversion of pyruvate to oxaloacetate, among other reactions. The biotin-dependent enzymes include pyruvate carboxylase, acetyl-CoA carboxylase, and propionyl-CoA carboxylase.

In contrast, thiamine (vitamin B1) is primarily associated with decarboxylation reactions and the metabolism of carbohydrates, while pyridoxine (vitamin B6) is involved in amino acid metabolism including transamination and decarboxylation. Niacin (vitamin B3) acts as a precursor for NAD and NADP, which are essential for redox reactions but not specifically for car