As other amino acids, it is an important component of cell proteins. Due to the chemical properties of its imidazole group, histidine forms part of the active center of numerous enzymes with acid-base catalytic activity. In addition, thanks also to its imidazole group, it is easily coordinated with metals (Ni, Zn, Cu) which increases the ability of plants to withstand stress situations produced by these metals. Thanks to histidine some plants can accumulate large amounts of nickel in the roots, it is believed that this hyper-accumulation of nickel has defensive properties against some plants.