Principles of Biochemistry (2+1)

10.1.5.Biotin

Biotin is an imidazole derivative widely distributed in natural food. A large portion of the human requirement for biotin is met by synthesis from intestinal bacteria, and hence biotin deficiency is caused not by simple dietary deficiency but by defects in utilization.

Function: Biotin is a coenzyme of carboxylase enzymes and functions as a component of specific multi–subunit enzymes that catalyze carboxylase reactions. A carboxylate ion is attached to the N1 of the biotin, generating an activated intermediate, carboxybiotin, attached to the biotin carrier protein. This step requires -HCO₃^- , ATP, Mg²⁺, and acetyl-CoA (as an allosteric effector). The activated carboxyl group is then transferred to the substrate of the reaction, e.g. pyruvate.

Deficiency: Biotin deficiency is not normally produced on account of bacterial synthesis in the intestinal tract. Consumption of raw eggs can cause biotin deficiency. Egg white contains a heat-labile protein, avidin, which combines very tightly with biotin, preventing its absorption and inducing biotin deficiency. The symptoms include depression, hallucinations, muscle pain, and dermatitis.

RDA

Since intestinal bacteria and diets supply biotin in adequate amounts the deficiency of this vitamin in human beings are rare.

 Infants :10-15µg

Children :20-40µg

Adults (male) :50-60µg

Sources 

Rich sources : Egg yolk, liver, kidney

Good sources: Yeast, milk, tomatoes. 

Fair sources  : Fruits, vegetable.