Biotin is a prosthetic group which binds to lysine of the enzyme via peptide bond. Biotin deficiency causes dermatitis and hair loss. This is usually caused not by lack of biotin in the diet. Instead, antivitamin, avidin, binds biotin and makes it unavailable for digestion and absorption. Raw egg white contains a lot of avidin.
Folic acid is the most prominent human vitamin deficiency.
The function of THEA is as transport vehicle for single carbon unit. This is important for purine synthesis and thymidylate synthesis, both are required for DNA synthesis and thus, cell replication. Folic acid deficiency will affect all mitotically active cells. These incudes hematopoietic cells and all epithelial cells. It is a potent antimicrobials in feeds.