Pantothenic acid

Pantothenic acid, also called vitamin B5.

PA is a water-soluble B vitamin and therefore an essential nutrient.

Pantothenic acid is required to synthesize coenzyme A (CoA) – essential for fatty acid metabolism – as well as to, in general, synthesize and metabolize proteins, carbohydrates, and fats.

It is a starting compound in the synthesis of coenzyme A (CoA), a cofactor for many enzyme processes.

Pantothenic acid is the combination of pantoic acid and β-alanine. 

Small quantities of pantothenic acid are found in nearly every food.

Deficiency is very rare.

As a dietary supplement, it is commonly used is calcium pantothenate because of chemical stability.

It is synthesized from the amino acid β-alanine and pantoic acid.

Bacteria synthesize pantothenic acid from the amino acids aspartate and a precursor to the amino acid valine. 

Aspartate is converted to β-alanine. 

The amino group of valine is replaced by a keto-moiety which, in turn, forms α-ketopantoate following transfer of a methyl group, then to D-pantoic acid following reduction. 

β-alanine and pantoic acid are then condensed to form pantothenic acid.

Unlike vitamin E or vitamin K, which occurs in several chemically related forms known as vitamers, pantothenic acid is only one chemical compound. 

PA is a precursor to CoA via a five-step process. 

CoA biosynthesis requires pantothenic acid, cysteine, four equivalents of ATP.

CoA is a competitive inhibitor of pantothenate kinase, the enzyme responsible for the first step.

Coenzyme A is necessary in the reaction mechanism of the citric acid cycle. 

The citric acid cycle is the body’s primary catabolic pathway.

The citric acid cycle is essential in breaking down the building blocks of the cell such as carbohydrates, amino acids and lipids, for fuel.

CoA is important in energy metabolism for pyruvate to enter the tricarboxylic acid cycle (TCA cycle) as acetyl-CoA, and for α-ketoglutarate to be transformed to succinyl-CoA in the cycle.

CoA is also required for acylation and acetylation, involved in signal transduction, and various enzyme functions.

CoA can act as an acyl group carrier to form acetyl-CoA and other related compounds; this is a way to transport carbon atoms within the cell.

CoA is also required in the formation of acyl carrier protein (ACP), which is required for fatty acid synthesis.

CoA synthesis also connects with other vitamins such as thiamin and folic acid.

The current intake for teens and adults ages 14 and up is 5 mg/day. 

For a typical diet, urinary excretion is approximately 2.6 mg/day, and that bioavailability of food-bound pantothenic acid  is  roughly 50%.

Intake for pregnancy is 6 mg/day, for lactation is 7 mg/day. 

For infants up to 12 months adequate intake is 1.8 mg/day. 

For children ages 1–13 years adequate intake increases with age from 2 to 4 mg/day. 

Adequate intake of pantothenic acid 

Infants 0–6 months 1.7 mg

Infants 7–12 months 1.8 mg

Children 1–3 years 2 mg

Children 4–8 years 3 mg

Children 9–13 years 4 mg

Adult men and women 14+ years 5 mg

Pregnant women 6 mg

Breastfeeding women 7 mg

Less formal estimates of adult daily intakes report about 4 to 7 mg/day.

There is no human data for adverse effects from high doses.

Food sources of pantothenic acid include animal-sourced foods, including dairy foods and eggs.

Potatoes, tomato products, oat-cereals, sunflower seeds, avocado, whole grains, and mushrooms are good plant sources. 

The milling of whole grains to make white rice or white flour removes much of the pantothenic acid.

The amount of pantothenic acid in dietary supplement products may contain up to 1,000 mg or 200 times the adequate Intake level for adults.

As a dietary supplement pantethine,, composed of two pantothenic acid molecules linked by a disulfide bridge, may be effective for lowering blood levels of LDL cholesterol.

Dietary supplementation with pantothenic acid does not have the same effect on LDL.

Pantothenic acid deficiency is so rare that it is not require to be fortified in food.

Most pantothenic acid is in the form of CoA or bound to acyl carrier protein,and 

for the intestinal cells to absorb it,it must be converted into free pantothenic acid. 

CoA and ACP are hydrolyzed in the intestinal lumen into 4′-phosphopantetheine, which is then dephosphorylated into pantetheine. 

Pantetheinase, an intestinal enzyme, then hydrolyzes pantetheine into free pantothenic acid.

Free pantothenic acid is absorbed into intestinal cells via a sodium-dependent active transport system.

At high levels of intake, some pantothenic acid may also be additionally absorbed via passive diffusion.

When  intake increases 10-fold, absorption rate decreases to 10%.

After its release from CoA pantothenic acid is excreted in urine. 

Urinary amounts are on the order of 2.6 mg/day.

Pantothenic acid deficiency in humans is very rare.

Deficiency has been seen prisoners of war during World War II, victims of starvation.

Symptoms of pantothenic acid deficiency are reversed with oral replacement.

Symptoms of pantothenic deficiency are similar to other vitamin B deficiencies: impaired energy due to low CoA levels, irritability, fatigue, and apathy.

With pantothenic deficiency acetylcholine synthesis is also impaired, and  neurological symptoms can also appear:  sensation of numbness in hands and feet, paresthesia and muscle cramps, restlessness, malaise, sleep disturbances, along with nausea, vomiting and abdominal cramps.

Pantothenic acid status is evaluated by measuring either whole blood concentration or 24-hour urinary excretion. 

Whole blood values less than 1 μmol/L are considered low, as is urinary excretion of less than 4.56 mmol/day.

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