histidine

histidine (hĭsˈtĭdēn) [key], organic compound, one of the 22 α-amino acids commonly found in animal proteins. Only the l -stereoisomer appears in mammalian protein. Histidine is the direct precursor of histamine; it is also an important source of carbon atoms in the synthesis of purines. The imidazole group on the side chain of histidine can act as both an acid and a base, i.e., it can both donate and accept protons under some conditions. This turns out to be an important property when histidine is incorporated into proteins, particularly when it becomes a part of the primary structure of some enzymes. It is thought that the side chain of this amino acid acts as a general acid and base as it participates in the catalytic functions of chymotrypsin, as well as those of a number of enzymes dealing with the metabolism of carbohydrates, proteins, and nucleic acids. It has even been implicated in the workings of cocoonase, the enzyme that allows adult silk moths to escape from their cocoons. Histidine is considered to be an essential amino acid for infants (it must be supplied in the diet); experiments with adults indicate that they can go for at least short periods without dietary intake of this amino acid. It was isolated from protein in 1896; its structure was confirmed by chemical synthesis in 1911.

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.

More on histidine from Fact Monster:

  • histamine - histamine histamine , organic compound derived in the body from the amino acid histidine by the ...
  • trypsin - trypsin trypsin, enzymethat acts to degrade protein; it is often referred to as a proteolytic ...
  • amino acid - amino acid amino acid , any one of a class of simple organic compounds containing carbon, hydrogen, ...
  • enzyme: Enzymatic Action - Enzymatic Action Like all catalysts, enzymes accelerate the rates of reactions while experiencing ...
  • Encyclopedia: Biochemistry - Encyclopeadia articles concerning Biochemistry.

See more Encyclopedia articles on: Biochemistry