Histamine degradation is mainly carried out by two enzymes in the human body:

  1. Diamine oxidase (DAO): This is a digestive enzyme that is found in the brush border of the small intestine. It is responsible for breaking down histamine in food.
  2. Histamine N-methyltransferase (HNMT): This is a cytosolic enzyme that is found in many tissues, including the liver, lungs, and brain. It acts by methylating histamine, which makes it more polar and easier to excrete.

Both DAO and HNMT are important in controlling histamine levels in the body and preventing histamine toxicity, which can occur in response to certain foods, drugs, or infections. Impaired histamine degradation has been linked to various medical conditions, such as allergies, migraines, and gastric disorders.