histidineen

Histidineen is not a recognized term in standard chemical or biochemical nomenclature. There is no widely accepted compound or concept by that name in major databases, journals, or reference works. It may be a misspelling of histidine, a fictional designation used in a particular context, or a shorthand in a specific study. Without additional context, a precise article cannot be given for histidineen itself. If you meant histidine, the following overview applies.

Histidine is an essential amino acid in humans with the chemical formula C6H9N3O2. It features an α-carboxyl group, an α-amino group, and a side chain containing an imidazole ring. The imidazole side chain has a pKa around 6.0, enabling histidine to act as a proton donor or acceptor near physiological pH and to participate in enzymatic catalysis and buffering. Histidine is encoded in the genetic code by the codons CAU and CAC. It can be metabolized to histamine via histidine decarboxylase, a process important in immune responses and neurotransmission. Histidine is found in a variety of protein-rich foods, including meat, fish, dairy, and legumes, and is typically supplied in sufficient amounts through a balanced diet.

In biology, histidine residues commonly participate in enzyme active sites and metal ion coordination, particularly with zinc in metalloproteins. Histidine-rich regions also feature in several proteins and can influence structure and function. In signal transduction, histidine kinases are a class of enzymes that utilize histidine phosphorylation within two-component signaling systems, especially in bacteria, archaea, and plants.

If you intended a different term, such as a histidine derivative or a fictional concept named histidineen, please provide more context for a more precise article. See also histidine and histamine.