Pantothenic acid (vitamin B5) is the B vitamin that is the precursor of coenzyme A (CoA) and of the acyl carrier protein (ACP) — the two cofactors that are the foundation of all acyl group metabolism in the body, including the synthesis and oxidation of fatty acids, the oxidation of pyruvate in the TCA cycle, the synthesis of cholesterol and steroid hormones, the acetylation of proteins and neurotransmitters, and the detoxification of drugs and xenobiotics by the cytochrome P450 system. Pantothenic acid is converted to CoA in a five-step pathway that requires ATP, cysteine, and magnesium as cofactors, and it is the CoA that is the metabolically active form of pantothenic acid. CoA is present in every cell in the body at concentrations of approximately 0.5-1mM, and it is the cofactor that is required for the function of over 100 enzymes that catalyse acyl group transfer reactions. Without adequate pantothenic acid, CoA synthesis is impaired, and every metabolic pathway that depends on CoA is compromised. This pantothenic acid-dependent vulnerability of acyl group metabolism is the foundation of the clinical syndrome of pantothenic acid deficiency — which includes the reversible dermatitis, the gastrointestinal symptoms, the fatigue, and the neuropsychiatric symptoms that are the hallmark of this deficiency.
Coenzyme A and Energy Metabolism
Coenzyme A is the cofactor that is required for the function of the acyltransferases and the dehydrogenases of the central metabolic pathways — including the pyruvate dehydrogenase complex (which converts pyruvate to acetyl-CoA, linking glycolysis to the TCA cycle), the alpha-ketoglutarate dehydrogenase complex (which converts alpha-ketoglutarate to succinyl-CoA in the TCA cycle), the fatty acid synthase complex (which uses malonyl-CoA to extend the growing fatty acid chain by two carbons at a time), the carnitine palmitoyltransferase system (which uses CoA to form the acylcarnitine esters that are the transport form of fatty acids into the mitochondrial matrix), and the acyl-CoA synthetases (which activate fatty acids for oxidation by attaching them to CoA). Without CoA, none of these central metabolic pathways can function, and the cell cannot generate ATP from glucose or from fatty acids. This makes pantothenic acid deficiency a metabolic emergency that is characterised by a failure of cellular energy production and by the systemic fatigue, weakness, and malaise that are the clinical manifestations of impaired energy metabolism.
The burning feet syndrome — the characteristic neurological manifestation of pantothenic acid deficiency — is thought to result from the impaired energy metabolism in the peripheral nerves, which are particularly sensitive to the loss of CoA-dependent metabolic pathways. The peripheral nerves rely heavily on aerobic metabolism for their energy needs, and when CoA is not available to support the TCA cycle and the electron transport chain, the nerves undergo a metabolic crisis that produces the burning pain, the numbness, and the paraesthesias that are the hallmark of this syndrome. The burning feet syndrome was first described in prisoners of war during World War II, who developed this characteristic neurological presentation in the context of severe malnutrition and pantothenic acid deficiency. The syndrome is reversible with pantothenic acid supplementation, which restores CoA levels and reverses the neurological symptoms within days to weeks.
Pantothenic Acid and Skin Health
Pantothenic acid is also essential for the health of the skin and for the wound healing process. The mechanism by which pantothenic acid supports skin health involves its role as a component of CoA, which is required for the synthesis of the fatty acids and of the sterols that are incorporated into the skin lipids, for the proliferation of fibroblasts and keratinocytes, and for the synthesis of the collagen and elastin fibres that are the structural components of the dermis. Pantothenic acid has been studied for its effects on wound healing — topical preparations containing dexpanthenol (the alcohol analogue of pantothenic acid, which is converted to pantothenic acid in the skin) have been shown to improve wound healing and to reduce the risk of wound dehiscence (the reopening of surgical wounds) after abdominal surgery. The mechanism of this wound healing effect is thought to involve the pantothenic acid-induced stimulation of fibroblast proliferation and of collagen synthesis.
Practical Application
For general pantothenic acid supplementation, the evidence-based dose is 5-10mg of pantothenic acid daily (as calcium pantothenate or pantethine, the two most common supplemental forms), which is approximately the RDA of 5mg daily for adults. For the treatment of skin conditions and for wound healing support, higher doses of 100-500mg daily may be used, with good evidence for their use in the management of acne, of the dermatological manifestations of biotin deficiency, and of the wound healing process. Pantothenic acid is generally well-tolerated with no significant adverse effects at therapeutic doses, though very high doses (above 10g daily) can produce diarrhoea. For comprehensive metabolic and skin health support, pantothenic acid pairs well with the other B-complex vitamins (which are required for the function of the CoA-dependent enzymes and for the metabolism of the central metabolic pathways), with vitamin D (which supports skin health and immune function), with zinc (which is required for collagen synthesis and for wound healing), and with the omega-3 fatty acids (which have anti-inflammatory effects in the skin and which support the integrity of the skin lipid barrier).
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