Castle's Intrinsic Factor

Literature References: A thermolabile mucoprotein with mol wt about 60,000. Promotes vitamin B12 absorption by transporting it through the intestinal wall. Occurs in normal gastric juice, but is deficient in patients with pernicious anemia. Prepd from hog mucosa: Castle et al., Am. J. Med. Sci. 178, 748, 764 (1929); 180, 305 (1930); Glass et al., Science 115, 101 (1952); Heinle et al., Trans. Assoc. Am. Physicians 65, 214 (1952); Latner et al., Biochem. J. 55, XXIII (1953); Callender et al., Br. Med. J. I, 10 (1954); Latner et al., Lancet I, 497 (1954); Baum, Federman, US 2912360 (1959 to Lilly). Purification: Robbins, US 3008877 (1961 to Armour); Highley, Ellenbogen, US 3434927 and US 3591678 (1969, 1971, both to Am. Cyanamid). In approx 30% of pernicious anemia patients, antibodies are produced in the serum which combine with IF, thus inhibiting its biological activity. In clinical tests diminished excretion of vitamin B12 in the feces is taken as evidence of intrinsic factor activity. Function in the metabolism of vitamin B12: Glass, Physiol. Rev. 43, 529 (1963). Review: Gräsbeck, Prog. Hematol. 6, 233 (1969).