Pantothenate

Pantothenate (pantothenic acid (R)-N-(2,4-dihydroxy-3,3-dimcihyl-l-oxobutyl)-beta-alanine. D( - F N-( 2,4-dihy droxy-3,3 -dim ei hy 1 bu tyry 1 )-bcta-a I an i ne, di hydroxy-beta, beta-d iraethylbutyry 1 -beta-alanine, vitamin B5. chick antidcrmatitis factor; molecular weight 219) is a water-soluble vitamin.

Abbreviations

Co A coenzyme A PANK pantetheine kinase

Nutritional summary

Function: Pantothenate is essential for fuel metabolism (especially of fat and alcohol). brain function (neurotransmitter and hormone synthesis), growth and regeneration (synthesis of membranes, heme, hormones, and functional proteins). Food sources: All food groups provide at least a modest amount of pantothenate. Good sources (at least 2()ui> of recommended intake per serving) include sweet potato, lentils, split peas, yoghurt, avocado, chicken, and liver. Relining of grains and overcooking of foods reduces their pantothenate content.

Requirements Adults should get about 5mg day (Food and Nutrition Board Institute of Medicine, 1998). Smoking, strenuous exercise, heat, infections, and injuries each may increase needs by 50% or more,

Deficiency: The widespread occurrence of pantothenate in all food groups makes inadequate intake by healthy people very unlikely. The interference by a few prescription drugs (antimetabolites), used in rare specific instances, can interfere with absorption and cause problems. The few people with confirmed deficiency (due to medication) had relatively mild and reversible symptoms, which included tingling sensations of toes and Icet, fatigue, vomiting, sleeplessness, and increased susceptibility to infections.

Excessive intake: No harmful effects of doses many times above recommended levels have been observed.

Dietary and other sources

Foods contain coenzyme A (CoA), 4-phosphopaniothenate. and pantothenate. Pantheno! may be consumed with dietary supplements. Good sources include liver, yeast, egg yolk, fresh vegetables, and bee royal jelly. About half of the pantothenate in meat, but not ¡11 vegetables, may be lost during cooking.

-Alanine

Panioic acid

Figure 10.42 Coenzyme A (CoA)

Pantetheine

Pantetheine

Coenzyme A

Average pantothenate consumption of Americans is about 10mg/2500 kcal. The amounts available from production by intestinal flora in the terminal ileum and colon are unknown, but are likely to be significant. This may explain why pantothenate deficiency symptoms are almost never observed, despite the critical importance of this vitamin fora broad spectrum of metabolic functions.

Digestion and absorption

Small doses of crystalline pantothenate are absorbed almost completely (Shibata el al„ 1983). Dietary CoA and simitar compounds can only be absorbed when digestive enzymes, including alkaline phosphatase (HC3.1.3,1) and pantetheine hydrolase (LC'3.5.1.-), release their pantothenate moieties.

The sodium-dependent multivitamin carrier (SLC5A6) is responsible for uptake of pantothenate into enterocytes of the small and large intestine. Pantothenate uptake via SLC5A6 is driven by two sodium ions, analogous to the mechanism of the structurally related sodium glucose eotransporter I (Prasad el ai. 2000). Several molecular variants of this carrier have been found in the small and large intestines (Chatterjee et ill.. 1999). The significance of this diversity is not yet understood. The sodium-dependent multivitamin carrier also mediates uptake ofbiotin and lipoate.

The mechanism of pantothenate transport across the basolateral membrane and onwards into portal blood has not been characterized as yet.

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