Пантотеновая кислота: свойства, метаболизм и применение

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| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 477003091
| ImageFile = (R) Pantothenic acid Formula V.1. svg
| ImageSize =
| ImageName = Skeletal formula of (R) pantothenic acid
| ImageFile1 = Pantothenic acid based on xtal 3D bs 17. png
| ImageSize1 =
| ImageName1 = Pantothenic acid molecule
| PIN = 3 [(2R) 2,4 Dihydroxy 3,3 dimethylbutanamido]propanoic acid
| SystematicName = 3 [(2R) (2,4 Dihydroxy 3,3 dimethylbutanoyl)amino]propanoic acid
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|Section2=Chembox Properties
| C=9 | H=17 | N=1 | O=5
| Density = 1.266 g/cm3 1.32 g/cm3 (Ca2+ salt)
| Appearance = Yellow oil Colorless crystals (Ca2+ salt)
| Odor = Odorless
| MeltingPtC = 183.833
| MeltingPt notes = decomposes (Ca2+ salt)
| pKa = 4.41
| pKb = 9.698
| Solubility = Very soluble 2.11 g/mL (Ca2+ salt) All animals need pantothenic acid in order to synthesize coenzyme A (CoA), which is essential for cellular energy production and for the synthesis and degradation of proteins, carbohydrates, and fats. Deficiency of pantothenic acid is very rare in humans. Pantothenic acid is phosphorylated to 4′ phosphopantothenate by the enzyme pantothenate kinase. This is the committed step in CoA biosynthesis and requires ATP. A cysteine is added to 4′ phosphopantothenate by the enzyme phosphopantothenoylcysteine synthetase to form 4' phospho N pantothenoylcysteine (PPC). This step is coupled with ATP hydrolysis. 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, which, for example, are involved in signal transduction, and various enzyme functions. which is required for fatty acid synthesis. Its synthesis also connects with other vitamins such as thiamin and folic acid.

The US Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for B vitamins in 1998. At that time there was not sufficient information to establish EARs and RDAs for pantothenic acid. In instances such as this, the Board sets Adequate Intakes (AIs), with the understanding that at some later date, AIs may be replaced by more exact information. The current AI for teens and adults ages 14 and up is 5 mg/day. This was based in part on the observation that for a typical diet, urinary excretion was approximately 2.6 mg/day, and that bioavailability of food bound pantothenic acid was roughly 50%. Less formal estimates of adult daily intakes report about 4 to 7 mg/day.

As for safety, the IOM sets Tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. In the case of pantothenic acid there is no UL, as there is no human data for adverse effects from high doses.

For US food and dietary supplement labeling purposes the amount in a serving is expressed as a percent of Daily Value (%DV). For pantothenic acid labeling purposes 100% of the Daily Value was 10 mg, but as of May 2016 it was revised to 5 mg to bring it into agreement with the AI. Compliance with the updated labeling regulations was required by January 2020 for manufacturers with US$10 million or more in annual food sales, and by January 2021 for manufacturers with lower volume food sales. A table of the old and new adult daily values is provided at Reference Daily Intake.

Food sources of pantothenic acid include animal sourced foods, including dairy foods and eggs. Potatoes, tomato products, oat cereals, sunflower seeds, avocado are good plant sources. Mushrooms are good sources, too. Whole grains are another source of the vitamin, but milling to make white rice or white flour removes much of the pantothenic acid, as it is found in the outer layers of whole grains. As a dietary supplement, pantothenic acid is not the same as pantethine, which is composed of two pantothenic acid molecules linked by a disulfide bridge.

When found in foods, most pantothenic acid is in the form of CoA or bound to acyl carrier protein (ACP). For the intestinal cells to absorb this vitamin, it must be converted into free pantothenic acid. Within the lumen of the intestine, CoA and ACP are hydrolyzed into 4' phosphopantetheine. The 4' phosphopantetheine 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 saturable, sodium dependent active transport system. they include sensation of numbness in hands and feet, paresthesia and muscle cramps. Additional symptoms could include restlessness, malaise, sleep disturbances, nausea, vomiting and abdominal cramps. In rodents, there can be loss of hair color, which led to marketing of pantothenic acid as a dietary supplement which could prevent or treat graying of hair in humans (despite the lack of any human trial evidence). Net microbial synthesis of pantothenic acid in the rumen of steer calves has been estimated to be 2.2 mg/kg of digestible organic matter consumed per day. Supplementation of pantothenic acid at 5 to 10 times theoretical requirements did not improve growth performance of feedlot cattle.

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 to yield α ketoisovalerate, which, in turn, forms α ketopantoate following transfer of a methyl group, then D pantoate (also known as pantoic acid) following reduction. β alanine and pantoic acid are then condensed to form pantothenic acid (see figure). Synthesis of the vitamin is completed by resolution of the lactone using quinine, for example, followed by treatment with the calcium or sodium salt of β alanine.

The term vitamin is derived from the word vitamine, which was coined in 1912 by Polish biochemist Casimir Funk, who isolated a complex of water soluble micronutrients essential to life, all of which he presumed to be amines. When this presumption was later determined not to be true, the "e" was dropped from the name, hence "vitamin". Vitamin nomenclature was alphabetical, with Elmer McCollum calling these fat soluble A and water soluble B. Three years later Elvehjem and Jukes demonstrated that it was a growth and anti dermatitis factor in chickens. Williams dubbed the compound "pantothenic acid", deriving the name from the Greek word pantothen, which translates as "from everywhere". His reason was that he found it to be present in almost every food he tested.