title: Atypical cobalamin binding in the serum of congenital deficiency of transcobalamin II.
abstract: The serum cobalamin (Cb 1) binding patterns were described in nine children with congenital deficiency of transcobalamin II (TC II). Immunoreactive TC II was less than 100 pg/ml TC II-Cb 1 equivalent in eight and 150 pg/ml in the ninth. There was neither endogenous TC II-Cb 1 (holo TC II) nor apo TC II. Thus, the defect was characterized by the absence of any binding of Cb 1 to TC II either in vivo or in vitro and either non-detectable or much reduced immunoreactive TC II. Only the serum from an untreated infant bound any added Cb 1 at all, but in every sera there was binding of endogenous Cb 1 to a substance of the molecular size of albumin. Native Cb 1 was also bound to R binder and in some instances was incorporated into large complexes. The precise nature, cause and consequences of this atypical binding are unknown.
mesh_terms: D000293:Adolescent; D001665:Binding Sites; D001798:Blood Proteins / Q000172:deficiency*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D011863:Radioimmunoassay; D014155:Transcobalamins / Q000172:deficiency*; D014805:Vitamin B 12 / Q000097:blood*
chemical_list: D001798:Blood Proteins; D014155:Transcobalamins; D014805:Vitamin B 12