Isolation and Characterization of an Abnormal Human Intrinsic Factor

Correction of Cobalamin Malabsorption in Pancreatic Insufficiency with a Cobalamin Analogue that Binds with High Affinity to R Protein but not to Intrinsic Factor

“…as previously described (4). Rabbit anti-human IF (13) and anti-human R protein (14) sera, purified human IF (13), and human anti-IF blocking antibodies (13) were obtained as described previously. Cbl binding assays were performed as described previously (13).…”

Effect of Proteolytic Enzymes on the Binding of Cobalamin to R Protein and Intrinsic Factor

“…5-ml fractions were collected and assayed for total Cbl-binding ability (18) and Cbl-binding ability due to IF (18 (16) and labeled with 1251 and "3Il by the method of Bolton and Hunter (19) as previously described (20). Rabbit anti-human IF (21) and anti-human R protein (16) sera were obtained as previously described. Association constants for Cbl-binding proteins and Cbl were determined at 37°C in standard incubation buffer using the charcoal adsorption technique as described (22 The ability of pancreatic proteolytic enzymes to alter the distribution and transfer of [57Co]Cbl between R protein and IF was studied by performing a 60-min preliminary incubation at 37°C with enzyme and various components of the standard assay.…”

Megaloblastic anemia as a result of an abnormal transcobalamin II (Cardeza).

“…These findings suggest that the two known Cbl-dependent reactions occur primarily or predominantly in tissues in which the mechanism for the uptake of Cbl may be different from that of the bone marrow. The increased amounts of TC II in our patient could bind Cbl and react with specific antibody but could not facilitate the uptake of the vitamin, which is analogous to the abnormal human intrinsic factor that could bind but could not facilitate the intestinal absorption of the vitamin (33). The uptake of TC 11-Cbl was tested in two systems: HeLa cells and stimulated lymphocytes.…”