pantothenic acid
Summary
Pantothenic acid (Vitamin B5) is a water-soluble vitamin essential for the synthesis of coenzyme A (CoA) and acyl carrier protein (ACP), critical cofactors in fatty acid metabolism and the citric acid cycle. Deficiency is rare but classically causes dermatitis, enteritis, alopecia, and adrenal insufficiency-like symptoms (dysesthesias, 'burning feet syndrome').
Detail
Pantothenic acid is a precursor for coenzyme A (CoA), which is required for the transfer of acyl groups in numerous metabolic reactions, including fatty acid oxidation and synthesis, the citric acid cycle (as acetyl-CoA and succinyl-CoA), amino acid catabolism, and cholesterol/steroid hormone synthesis. It also serves as a component of acyl carrier protein (ACP), essential for fatty acid synthase activity. Pantothenic acid is widely distributed in foods (meat, whole grains, avocados), so isolated deficiency is extremely rare and typically only seen in severe malnutrition. Clinical features of deficiency, when they occur, include dermatitis, enteritis, alopecia, adrenal insufficiency, and a distinctive symptom called 'burning feet syndrome' characterized by paresthesias and dysesthesias of the feet. On USMLE exams, pantothenic acid is often tested in the context of vitamin B-complex overview questions, with emphasis on its role as a CoA precursor and mnemonic associations (B5 = 5 carbons in CoA-related structure, 'Pantothen-A' for coenzyme A synthesis).
Sources
- First Aid for the USMLE Step 1
- Lippincott Illustrated Reviews: Biochemistry
- Harper's Illustrated Biochemistry
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