Title: Ricin
CAS Registry Number: 9009-86-3
Literature References: A toxic lectin and hemagglutinin isolated from castor bean, Ricinus communis L., Euphorbiaceae: Stillmark, Arb. Pharmak. Inst. Dorpat 1889, 59; T. Osborne et al., Am. J. Physiol. 14, 259 (1905); H. L. Craig et al., US 3060165 (1962 to U.S. Dept. Army). Purification of toxic ricin protein: M. Ishiguro et al., J. Biochem. 55, 587 (1964). The hemagglutinating activity of ricin was initially believed to be the cause of its high toxicity, but later studies have shown that separate proteins are responsible for the toxicity and hemagglutination: S. Olsnes, A. Pihl, Biochemistry 12, 3121 (1973). "Ricin", the original term for the mixed extract, is now used in various ways. Two ricin agglutinins and two toxins have been identified: RCL I, RCL II (agglutinins), RCL III or Ricin D and RCL IV (toxins), cf. T. T. Lin, S. S. Li, Eur. J. Biochem. 105, 453 (1980). All four lectins consist of two different polypeptide chains joined by a disulfide bond; the toxins are dimers of an A-chain (30,000 Da) and a B-chain (33,000 Da) and the agglutinins occur as a tetramer composed of two 30,000 and two 33,000 mol wt subunits. Ricin has been shown to have anti-tumor properties: J. Y. Lin et al., Nature 227, 92 (1970); P. E. Thorp et al., ibid. 297, 594 (1982). Synergistic effect with daunorubicin, cisplatin, and vincristine, q.q.v., in systemic L 1210 leukemia: O. Fodstad, A. Pihl, Cancer Res. 42, 2152 (1982). Conjugates of ricin and cell-binding antigens or antibodies, called immunotoxins, have been used in cancer therapy: E. S. Vitetta et al., Science 219, 644 (1983). Experimental study with ricin-A chain conjugate in AIDS: M. A. Till et al., Science 242, 1166 (1988). RIA determn in blood: A. Godal et al., J. Toxicol. Environ. Health 8, 409 (1981). Reviews: M. Funatsu, "The Structure and Toxic Function of Ricin" in Proteins, Structure and Function vol. 2, M. Funatsu et al., Eds. (Kodansha, Tokyo, Wiley, New York, 1972) pp 103-139; G. A. Balint, Toxicology 2, 77-122 (1974); C. Winder, J. Toxicol. Toxin Rev. 23, 97-103 (2004). See also Abrin, Lectins.
Properties: Isoelectric pt 7.1. uv max: 280 nm (e 85000). MLD i.p. in mice at 48 hrs: 0.001 mg ricin nitrogen/g body wt (Ishiguro).
Absorption maximum: uv max: 280 nm (e 85000)
Toxicity data: MLD i.p. in mice at 48 hrs: 0.001 mg ricin nitrogen/g body wt (Ishiguro)
CAUTION: Ricin is among the most toxic compounds known. Seeds of R. communis, if thoroughly masticated, can produce serious poisoning and death: J. M. Kingsbury, Poisonous Plants of the United States and Canada (Prentice-Hall, New Jersey, 1964) pp 194-197. Potential symptoms of overexposure by inhallation are weakness, fever, cough, pulmonary edema, respiratory distress, hypoxia; by ingestion are abdominal pain, GI hemorrhage, liver, spleen and kidney damage (Widner).
Use: As a tool in studies of cell-surface properties; exptly in cancer research.

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