The major protein constituent (75%) of egg white from hen's eggs. Mol wt about 45,000. Produced under hormonal control by the bird oviduct. May be isolated and crystallized readily from the filtrate of an acidified mixture of egg white and an equal volume of satd. ammonium sulfate: Sorensen, Hoyrup, C. R. Trav. Lab. Carlsberg 12, 12 (1917). Alternate method: Kekwick, Cannan, Biochem. J. 30, 227 (1936). Can be separated by electrophoresis and chromatography from about ten other minor components including avidin, lysozyme, conalbumin, q.q.v., and ovomucoid. Structure is a complex protein consisting of a single polypeptide chain of about 400 residues (about half of which are hydrophobic), a maximum of two phosphate residues per mole, and an oligosaccharide side chain composed of only mannose and glucosamine residues. Sequences of N- and C-terminal segments: Narita, Ishii, J. Biochem. 52, 367 (1962); Thompson et al., Aust. J. Biol. Sci. 24, 525 (1971). Reviews: R. C. Warner in Neurath-Bailey, The Proteins vol. II, part A (New York, 1954) p 443 sqq; Taborsky, Adv. Protein Chem. 28, 34-50 (1974).