One of the 20 amino acids that make up proteins.
histidine, His, amino acid, protein, peptide, polypeptide, polar side chain, zwitterionic structure, peptide bond, amide bond, amino acid sequence, molecule, organic chemistry, chemistry, biology, biochemistry
Molar mass: 155.15 g/mol
Melting point: 282 °C (539.6 °F)
Boiling point: 458 °C (856.4 °F)
Density: 1.423 g/cm³ (0.0514 lb/in³)
Histidine is a semi-essential amino acid. It is a colorless, crystalline substance that is well soluble in water, weakly soluble in ethanol and insoluble in ether. It is an important constituent of hemoglobin. Decarboxylation of histidine results in histamine.
Occurrence and production
Histidine occurs in free form in plants, but it is abundant in bound form in proteins, such as casein, fibrin, keratin and the proteins found in egg whites. Histidine synthesis and breakdown are complex processes.
Histidine is a building block of proteins.