Biotin is a made of a covalent linkage to epsilon-amino group of lysine in the enzyme active site.
Biotin is the active form of the vitamin while biocytin is when biotin is covalently linked to lysine, so when it is consumed the first step is to remove the lysine from the biotin.
Functions Biotin plays an important role in the metabolism of carbon dioxide (carboxylation reactions).
The reactions all require ATP and CO2.
1.
Acetyl-CoA Carboxylase-fatty acid synthesis: Acetyl-CoA + CO2 Malonyl-CoA 2.
Pyruvate Carboxylase-pyruvate to oxaloacetate, gluconeogenesis 3.
Propionyl CoA Carboxylase-odd chain fatty acid oxidation: Propionyl-CoA + CO2 methylmalonyl-CoA succinyl-CoA This is a two-step reaction and also requires vitamin B12 to convert the 3 carbon propionyl CoA to succinyl-CoA which can then be used in the TCA cycle to make energy for the body.
4.
beta-methylcrotonyl CoA Carboxylase-leucine degradation pathway This reaction allows the body to metabolize leucine and to get rid of it from the body.
Deficiency Biotin deficiencies rarely occur.
A biotin deficiency can be induced by certain medications and/or dietary conditions.
For example, a deficiency can be induced by eating raw egg whites; the whites contain the protein avidin that will bind with biotin and prevent it from being absorbed.
However, for this to happen one must consume around two dozen egg whites daily in order for this to have an effect.
Certain antidepressant, antibotic and anti-convulsant drugs may cause a biotin deficiency along with long-term hemodialysis.
Deficiency Symptoms include: o increased excretion of organic acids (aren't carboxylated or used for energy) o acidosis and ketosis o Gross deficiency o scaly dermatitis o tongue papillae o grey mucous membranes o depression Sources Significant sources of biotin can be found in a variety of foods and is also made by our intestinal bacterial.
Those with the largest amounts include: o yeast extracts o organ meats o egg yolks o soybeans o fish o tomato o rice o whole grains