Strepogenin

Literature References: A name for the biologically active principle capable of stimulating growth of certain microorganisms, and originally found present in products of natural origin, such as liver extract, flour, yeast, and tomato juice. Its peptide nature was indicated by its presence in hydrolyzates of purified proteins. To compare the activities of various protein hydrolyzates, a strepogenin unit was introduced and defined as: 1 mg of a standard liver extract (Wilson's liver fraction L) has the strepogenin activity of one unit (using Lactobacillus casei as test organism). The different structures of strepogenin-active peptides subsequently obtained from natural sources or by synthesis, indicate that strepogenin is not a distinct, chemically defined, biologically active peptide, but rather represents a biological phenomenon of a multitude of peptides. From the large number of strepogenin-active peptides known, no conclusion can be drawn with regard to structure-function relationships; these peptides have been suspected to be nothing more than easily accessible amino acids, particularly since they (peptides) are not essential for the growth of the microorganisms. Early isolation from liver extract and from tryptic digests of pure proteins: Sprince, Woolley, J. Exp. Med. 80, 213 (1944); eidem, J. Am. Chem. Soc. 67, 1734 (1945). Review: E. Schröder, K. Lübke, The Peptides vol. II (Academic Press, New York, 1966) pp 267-270.