L-Histidine (His) is an essential amino acid displaying a unique properties profile, involved in a number of biological activities, e.g. in pH buffering, in metal ion chelation, and in oxidative species scavenging, which confer it many physiological properties as antioxidant, anti-inflammatory, and in erythropoiesis and immune system regulation.

While there are several pathways of His degradation, most catabolism is directed to protein turnover and glutamate production and begins with histidase-dependent deamination. Also, the minor pathways of His as a precursor of histamine and His-rich proteins and peptides make it unique among other amino acids.