Essential amino acid for human development; precursor to histamine and a component of carnosine, q.v. Independently isolated in 1896 by both A. Kossel and S. G. Hedin, Zeit. Physiol. 22, 176, 191 (1896). Early chemistry and biochemistry: Amino Acids and Proteins, D. M. Greenberg, Ed. (Charles C. Thomas, Springfield, IL, 1951) 950 pp., passim; J. P. Greenstein, M. Winitz, Chemistry of the Amino Acids vols 1-3 (John Wiley and Sons, Inc., New York, 1961) pp. 1971-1995, passim. NMR spectra: D. H. Sachs et al., J. Biol. Chem. 246, 6576 (1971). HPLC determn in dipeptides: E. Kasziba et al., J. Chromatogr. 432, 315 (1988). Often found at the active site of proteins: W. T. Morgan et al., J. Biol. Chem. 268, 6256 (1993); J.-W. P. Boots et al., Biochim. Biophys. Acta 1248, 27 (1995). Role in proton translocation a model: J. E. Morgan et al., J. Bioenerg. Biomembr. 26, 599 (1994). Review of metabolism: F. B. Stifel, R. H. Herman, Am. J. Clin. Nutr. 24, 207-217 (1971). Review of role in nutrition: eidem, ibid. 25, 182-185 (1972); L. P. Mercer et al., Nutrition 6, 273-277 (1990).