BIOCHEMISTRY - Textbook - Ostapchenko L. I. - 2012

Chapter 8. VITAMINS

8.3. Water-soluble vitamins

8.3.5. Vitamin B₅ — pantothenic acid

Structure and physicochemical properties. Pantothenic acid is an amide of α,γ-dihydroxy-β,β-dimethylbutyric acid (pantoic acid) and β-Alanine (Fig. 8.17, A). It is a light yellow substance, highly soluble in Water, and easily hydrolyzed by the action of alkalis and acids.

It performs its biological role by forming compounds with substances containing a sulfhydryl group. For example, pantetheine, a thioethanolamide of pantothenic acid, acts as a growth factor for certain Bacteria. In The Human Body, pantothenic acid is a component of coenzyme A (CoA), an acyl carrier coenzyme, and 4'-phosphopantetheine, the prosthetic group of palmitate synthase.

Lipmann first isolated the substance required for acylation reactions from Liver tissue and named it coenzyme A (Fig. 8.17, B).

Biochemical Functions. The synthesis of coenzyme A begins with the phosphorylation of the vitamin and involves steps such as the attachment of Cysteine, its decarboxylation, linkage with AMP, and ribose phosphorylation. Coenzyme A participates in the activation of Fatty acids on the outer mitochondrial membrane, in fatty acid β-oxidation reactions, lipid synthesis, and acetylcholine synthesis. As part of pantetheine phosphate, the vitamin is also a component of the acyl carrier protein (ACP), a key component of the fatty acid synthesis system.

Requirement and natural occurrence. Vitamin deficiency is rare because pantothenic acid is widely distributed in both PLANT AND ANIMAL foods. Its deficiency leads to dermatitis, depigmentation of Hair and fur, and alopecia. The vitamin is heat-sensitive, with 30–40 % being destroyed during food thermal Processing. Rich sources include Yeast, milk, liver, eggs, and whole wheat flour. The daily requirement is 10–12 mg.

Class="center">

Fig. 8.17. Pantothenic acid (A) and coenzyme A (B)