Mycotoxins: the pathway in the body

This page shows the biochemical pathway behind the laboratory value Moulds / mycotoxins: 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

Mycotoxins are substances that some moulds form on foods, such as aflatoxin B1 and ochratoxin A. In the body, liver enzymes convert them; the products are bound to glutathione and leave with urine and stool.

The pathway step by step

1. Moulds → Aflatoxin B1 Fungal enzymes Aflatoxin B1 is made by a long chain of fungal enzymes. It largely withstands heat and is absorbed into the blood in the small intestine. Source 1, 2
2. Aflatoxin B1 → Aflatoxin epoxide CYP1A2, CYP3A4 · NADPH, oxygen In the liver, the enzymes CYP1A2 and CYP3A4 attach an oxygen atom as a ring. This form is highly reactive and readily combines with proteins and genetic material. Source 2, 3
3. Aflatoxin epoxide → Glutathione conjugate Glutathione S-transf. · glutathione (GSH) Glutathione S-transferases attach glutathione to the epoxide. This neutralises its reactive site and makes it water-soluble. Source 3, 2
4. Glutathione conjugate → Mercapturic acid γ-GT, N-acetyltransf. Further enzymes shorten the conjugate and add an acetyl group. The resulting mercapturic acid leaves the body in the urine. Source 3
5. Ochratoxin A → Bound to albumin · albumin In the blood, ochratoxin A is almost entirely bound to albumin. It is excreted in bile, reabsorbed in the gut and therefore stays in circulation for a long time. Source 4
6. Bound to albumin → Ochratoxin α Carboxypeptidase A Carboxypeptidase A from the pancreas and enzymes of gut bacteria cleave off the phenylalanine. What remains is ochratoxin α. Source 4, 5
7. Ochratoxin α → Excretion Ochratoxin α and a smaller share of unchanged ochratoxin A leave the body in urine and stool. Both can be detected there. Source 5

Cofactors in this pathway

• Glutathione — Glutathione S-transferases attach it to the aflatoxin epoxide and make it water-soluble Source 3, 2In the ORY catalogue as a laboratory value: Glutathion (GSH)
• NADPH — Electron donor of the cytochrome P450 enzymes CYP1A2 and CYP3A4 Source 2, 6
• Oxygen — Provides the oxygen atom that the P450 enzymes attach as an epoxide or OH group Source 2, 3
• Iron — Central atom in the haem of the cytochrome P450 enzymes Source 6In the ORY catalogue as a laboratory value: Eisen
• Vitamin B2 (FAD, FMN) — Flavin cofactors of P450 reductase, which passes electrons from NADPH to the P450 enzymes Source 6
• Zinc — Metal in the active site of carboxypeptidase A, which separates ochratoxin A into two parts Source 7, 4In the ORY catalogue as a laboratory value: Zink
• Acetyl-CoA — Donor of the acetyl group in the last step towards the mercapturic acid Source 3

Sources

1. Sweeney MJ, Dobson AD. Molecular biology of mycotoxin biosynthesis. FEMS Microbiol Lett 1999 · PubMed 10386364
2. Dohnal V, Wu Q, Kuča K. Metabolism of aflatoxins: key enzymes and interindividual as well as interspecies differences. Arch Toxicol 2014 · PubMed 25027283
3. Deng J, Zhao L, Zhang NY et al. Aflatoxin B(1) metabolism: Regulation by phase I and II metabolizing enzymes and chemoprotective agents. Mutat Res Rev Mutat Res 2018 · PubMed 30454686
4. Ringot D, Chango A, Schneider YJ, Larondelle Y. Toxicokinetics and toxicodynamics of ochratoxin A, an update. Chem Biol Interact 2006 · PubMed 16293235
5. Duarte SC, Pena A, Lino CM. Human ochratoxin a biomarkers--from exposure to effect. Crit Rev Toxicol 2011 · PubMed 21401326
6. Iyanagi T, Xia C, Kim JJ. NADPH-cytochrome P450 oxidoreductase: prototypic member of the diflavin reductase family. Arch Biochem Biophys 2012 · PubMed 22982532
7. Kim DH. Chemistry-based design of inhibitors for carboxypeptidase A. Curr Top Med Chem 2004 · PubMed 15320722

Related pathways

• Glutathione — mercapturic acid
• 8-OHdG — Glutathion (GSH), Eisen
• Copper — Glutathion (GSH), Eisen
• Borrelia — Eisen, Zink
• Calprotectin — Eisen, Zink

As of 2026-09-16. Draft written by Claude to schema v2; sources checked in PubMed; expert approval pending
Legal notice Privacy policy All biomarkers