A young adult consuming large quantities of raw egg white over several weeks develops dermatitis, alopecia, and conjunctivitis. The underlying mechanism involves:

• A Chelation of zinc by phytate present in egg white
• B Irreversible inhibition of pyridoxal phosphate by ovomucoid protease inhibitor
• C Binding of biotin by avidin, preventing intestinal absorption of the vitamin ✓
• D Competitive inhibition of riboflavin uptake by ovalbumin peptides

Explanation

Raw egg white contains avidin, a glycoprotein that binds biotin with extremely high affinity, rendering the vitamin unavailable for absorption across the intestinal brush border. Chronic consumption therefore produces true biotin deficiency manifesting as dermatitis, alopecia and neurological symptoms. Cooking denatures avidin and abolishes this effect. Biotin is the coenzyme of four carboxylases, namely pyruvate carboxylase, acetyl-CoA carboxylase, propionyl-CoA carboxylase and 3-methylcrotonyl-CoA carboxylase.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.