Histaminase

Histaminase is an enzyme that catalyzes the degradation of histamine, a biogenic amine with various physiological roles. Histamine is produced by the decarboxylation of histidine, a process catalyzed by histidine decarboxylase. Histaminase is found in various tissues and organs, including the liver, lungs, and skin, and is also present in certain microorganisms and plants. It plays a crucial role in regulating histamine levels in the body, which can affect various physiological processes, such as inflammation, allergic reactions, and neurotransmission.

There are two main types of histaminase: diamine oxidase (DAO) and histamine N-methyltransferase (HNMT). DAO is a copper-containing enzyme that oxidizes histamine to imidazole acetic acid and ammonia. HNMT, on the other hand, is a methyltransferase that transfers a methyl group from S-adenosylmethionine to histamine, forming N-methylhistamine. Both enzymes help to regulate histamine levels in the body, with DAO being the primary enzyme involved in histamine degradation in most tissues.

Histaminase inhibitors are used in the treatment of histamine-related disorders, such as allergic rhinitis and urticaria. These inhibitors can help to increase histamine levels in the body, thereby reducing symptoms associated with histamine excess. However, the use of histaminase inhibitors should be done with caution, as they can also have side effects, such as increased histamine levels in the brain, which can lead to central nervous system symptoms.