Vitamin H, C10 H16 O3 N25; a necessary constituent of the diet and an essential co-factor for certain enzymes catalizing reactions. It is covalently bound to enzyme protein through a lysien residue. Biotin-containing enzymes are inhibited by the egg-white protein, avidum, due to specific interaction with biotin. Deficiency is associated with dermatitis, loss of apetite and lassitrude.