Category: amino-acid
Aliases: His, H, L-Histidine
Imidazole side chain (pKa ~6.0) confers catalytic proton-shuttling activity in enzyme active sites — the dominant proton donor/acceptor at physiologic pH. Histamine precursor (via histidine decarboxylase). Component of carnosine (β-Ala-His) in skeletal muscle — buffers lactate-derived H⁺.