Synthesis and metabolism
Histamine is derived from the
decarboxylation of the
amino acid histidine, a reaction
catalyzed by the
enzyme L-histidine decarboxylase. It is a
hydrophilic vasoactive amine.
Conversion of
histidine to histamine by
histidine decarboxylase
Once formed, histamine is either stored or rapidly inactivated by its primary
degradative enzymes,
histamine-N-methyltransferase or
diamine oxidase. In the central nervous system, histamine released into the
synapses is primarily broken down by
histamine-N-methyltransferase, while in other tissues both enzymes may play a role. Several other enzymes, including
MAO-B and
ALDH2, further process the immediate metabolites of histamine for excretion or recycling.
Bacteria also are capable of producing histamine using histidine decarboxylase enzymes unrelated to those found in animals. A non-infectious form of foodborne disease,
scombroid poisoning, is due to histamine production by bacteria in spoiled food, particularly fish. Fermented foods and beverages naturally contain small quantities of histamine due to a similar conversion performed by fermenting bacteria or yeasts.
Sake contains histamine in the 20–40 mg/L range;
wines contain it in the 2–10 mg/L range.
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