Vitamin E: the pathway in the body

This page shows the biochemical pathway behind the laboratory value Vitamin E (tocopherol): which stations follow one another, which enzymes carry out each step and which cofactors they use. Every statement has a source. The page describes general textbook knowledge and says nothing about any individual person.

In brief

Vitamin E is the collective name for eight fat-soluble compounds, of which alpha-tocopherol is the most abundant in blood. In cell membranes it stops chain reactions of fatty acid radicals.

The pathway step by step

1. Vitamin E in food → Micelles in small bowel Lipases, esterases · Bile acids Bile acids and fat-splitting enzymes from the pancreas break down dietary fats. In the process, vitamin E moves into small fat droplets called micelles. Source 1
2. Micelles in small bowel → Into the gut cell NPC1L1, SR-BI Transport proteins in the surface of the gut cell, including NPC1L1 and SR-BI, absorb vitamin E from the micelles. Source 1
3. Into the gut cell → Chylomicrons · Dietary fats The gut cell packs vitamin E together with fats into chylomicrons. These reach the blood via the lymph, and their remnants travel on to the liver. Source 1
4. Chylomicrons → α-Tocopherol in VLDL α-TTP In the liver, α-tocopherol transfer protein (α-TTP) selectively picks out α-tocopherol and passes it to VLDL. The other forms are preferentially broken down, so α-tocopherol is the most common form in blood. Source 2, 1
5. Lipid peroxyl radical → Lipid hydroperoxide α-Tocopherol gives its hydrogen atom to the peroxyl radical; this becomes a lipid hydroperoxide, and the chain reaction stops. A tocopheroxyl radical remains, which vitamin C can convert back. Source 3
6. α-Tocopherol → 13'-Hydroxychromanol CYP4F2 · NADPH, Oxygen In the liver, the enzyme CYP4F2 attaches an OH group to the end of the long side chain. This starts the breakdown of the tocopherols. Source 5, 4
7. 13'-Hydroxychromanol → 13'-Carboxychromanol Dehydrogenases Dehydrogenases turn the OH group into an acid group. The side chain is thus ready for further breakdown. Source 4, 5
8. 13'-Carboxychromanol → α-CEHC β-oxidation The side chain is shortened step by step (β-oxidation), leaving α-CEHC. This water-soluble compound is linked to sulphate or glucuronic acid and excreted via urine and bile. Source 4

Cofactors in this pathway

• Vitamin C — Converts the tocopheroxyl radical back into alpha-tocopherol Source 3In the ORY catalogue as a laboratory value: Vitamin C (Ascorbinsäure)
• Bile acids — Form micelles with dietary fats from which the gut cell absorbs vitamin E Source 1In the ORY catalogue as a laboratory value: Gallensäuren (Stuhl)
• Selenium — Component of glutathione peroxidases, which further convert lipid hydroperoxides Source 7In the ORY catalogue as a laboratory value: Selen
• Glutathione — Supplies glutathione peroxidases with the electrons for this Source 7In the ORY catalogue as a laboratory value: Glutathion (GSH)
• NADPH — Supplies CYP4F2 with the electrons for the first breakdown step Source 5

What acts on this pathway

• Orlistat — Orlistat inhibits the fat-splitting lipases in the gut. Review articles describe that fat-soluble vitamins from food are then also absorbed to a lesser extent. Source 6

Sources

1. Rigotti A. Absorption, transport, and tissue delivery of vitamin E. Mol Aspects Med 2007 · PubMed 17320165
2. Arai H, Kono N. α-Tocopherol transfer protein (α-TTP). Free Radic Biol Med 2021 · PubMed 34563650
3. Traber MG, Atkinson J. Vitamin E, antioxidant and nothing more. Free Radic Biol Med 2007 · PubMed 17561088
4. Schmölz L, Birringer M, Lorkowski S et al. Complexity of vitamin E metabolism. World J Biol Chem 2016 · PubMed 26981194
5. Parker RS, Sontag TJ, Swanson JE et al. Discovery, characterization, and significance of the cytochrome P450 omega-hydroxylase pathway of vitamin E catabolism. Ann N Y Acad Sci 2004 · PubMed 15753130
6. Filippatos TD, Derdemezis CS, Gazi IF et al. Orlistat-associated adverse effects and drug interactions: a critical review. Drug Saf 2008 · PubMed 18095746
7. Jomova K, Alomar SY, Alwasel SH et al. Several lines of antioxidant defense against oxidative stress: antioxidant enzymes, nanomaterials with multiple enzyme-mimicking activities, and low-molecular-weight antioxidants. Arch Toxicol 2024 · PubMed 38483584

Related pathways

• APOE — chylomicrons
• Cholesterol and lipoproteins — chylomicrons
• Trans fatty acids — chylomicrons
• Triglycerides — chylomicrons
• 8-OHdG — Vitamin C (Ascorbinsäure), Selen

As of 2026-09-16. Draft written by Claude to schema v2; sources checked in PubMed; expert review pending
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