Mycotoxins

Question 1

Mycotoxins

Answer 1

Toxic compounds produced by fungi that contaminate food causing health risks.

Question 2

Aflatoxins

Answer 2

Highly toxic mycotoxins produced by Aspergillus sp. found in maize and peanuts, causing liver damage and cancer.

Question 3

Amanitins

Answer 3

Toxic compounds produced by fungi Amanita (death cap) leading to liver and kidney failure.

Question 4

Chemical nature of aflatoxins

Answer 4

Aflatoxins are polyketide-derived, small and hydrophobic with a fused coumarin-lactane structure, allowing for lipid penetration.

Question 5

Chemical nature of amanitins

Answer 5

Octapeptide backbone with unusual amino acid bnding to a tryptathione bridge, making them highly resistant to enzymatic degradation.

Question 6

Mechanism of aflatoxins

Answer 6

1. Ingestion: Aflatoxins enter gut
2. Absorption: Metabolized in liver by cytochrome P450 enzymes.
3. Toxic metabolites: Form reactive intermediates
4. DNA binding: Causes mutations
5. Liver damage: Leads to hepatocyte death, cirrhosis, or hepatocellular carcinoma.

Question 7

Mechanisms of amanitins

Answer 7

1. Ingestion: Amanitin enters the bloodstream
2. Hepatocyte uptake: Transported to the liver
3. RNA polymerase II inhibition: Blocks mRNA synthesis
4. Hepatocyte damage: oxidative stress
5. Liver failure: widespread hepatocyte necrosis.

Question 8

Two Aspergillus species that make aflatoxins

Answer 8

Aspergillus flavus - aflatoxin B1 most deadly
Aspergillus parasiticus - multiple types.

Question 9

Categorification of Alatoxins

Answer 9

Categories are done based on UV light.

Question 10

Categories of aflatoxins

Answer 10

AFB1 - most toxic an carcinogenic
AFB2 - slightly less toxic AFB1
AFG1 - green fluorescence of AFB1
AFG2 - slightly less toxic AFG1
AFM1 - Hydroxylated metabolite of AFB1, found in milk.

Question 11

Types of P450 enzyme

Answer 11

CYP1A2 and CYP3A4, which convert AFB1 to aflatoxin-8,9-epoxide, causing liver damage.

Question 12

AFB1 adduct

Answer 12

AFB1-N7-guanine which disrupts base pairing, specifaclly in p53 tumour suppressor.

Question 13

Oxidative stress

Answer 13

Reactive oxygen species cause lipid peroxification, DNA lyses.

Question 14

Proteinsynthesis inhibition.

Answer 14

Reduced ribosomal functions induces incorrect protein creation.

Question 15

Apoptosis induction

Answer 15

AFBI can increase production of pro-apoptopic pathways.