Histidine (His (also H))

Histidine is a dietary essential amino acid with the chemical formula C₆H₉N₃O₂. It contains an imidazole side chain, allowing it to act as a proton donor and acceptor near physiological pH. This makes it vital for enzyme catalysis, particularly in charge relay systems (catalytic triads), metal ion coordination (especially zinc), and pH buffering. Histidine is fundamental for protein synthesis in all tissues, hemoglobin function, mineral absorption, immune balance, and the synthesis of histamine, a critical mediator in inflammation and brain signaling. It is present in nearly all protein-rich foods and is required for normal growth and metabolic activity. Supplementation must be approached cautiously, as excessive intake can cause metabolic and neuropsychiatric side effects.

Other names

L-Histidinea-amino-b-[4-imidazole]-propionic acidGlyoxaline-5-alanineSymbol: His, H

Not applicable for drugs as it is not a target; however, drugs affecting histidine-derived pathways (e.g., antihistamines) target downstream molecules.