Megalin is an endocytic receptor with a high affinity for the Cbl transport protein transcobalamin
II that can mediate Cbl cellular uptake through endocytosis of the transcobalamin
II-Cbl complex .
18 Vitamin B12 levels may be reported as normal or elevated in myeloproliferative disorders liver disease congenital transcobalamin
II deficiency intestinal bacterial overgrowth and antecedent administration of vitamin B12.
Carmel reported that the blacks have significantly higher cobalamin and transcobalamin
II) levels than whites do while the lowest levels were observed in India, Africa, and Pakistan (5).
3 Good syndrome is among the long list of immunodeficiency differentials which include immunodeficiency due toHIV/AIDS, X linked agammaglobulinaemia (XLA), Autosomal Recessive Agammaglobulinemia, Selective IgM Deficiency, Selective IgE Deficiency, Antibody Deficiency with Transcobalamin
II Deficiency, Drug-Induced Antibody Deficiency, Interferon-a/IL-12 Pathway Deficiencies, Natural Killer Cell Deficiency, Phagocyte Killing Defects, Specific Granule Deficiency.
TCN2 encodes for transcobalamin
II which binds and transports vitamin B12 into the cell (Regec et al.
Blood was collected at baseline for measurement of plasma vitamin B(12), transcobalamin
(TC), holotranscobalamin (holoTC), methylmalonic acid (MMA), total homocysteine (tHcy), and serum folate.
12] binding by transcobalamin
II increases the risk of neural tube defects.
gene deletions/polymorphisms) and ASDs, including reduced folate carrier (RFC); catechol-O-methyltransferase (COMT); transcobalamin
II (TCN2); glutathione S-transferase M1 (GSTM1); glutathione S-transferase P1 (GSTP1); 5, 10-methylenetetrathydrofolate reductase (MTHFR); metal-regulatory transcription factor 1 (MTF1); and divalent metal ion transporter SLCllA3 (116, 114-117).
After three to four hours, the vitamin B12 appears in the blood carried on transcobalamin
Direct assay for cobalamin bound to transcobalamin
(holo-trascobalamin) in serum.
The intrinsic-factor cobalamin complex enters the intestinal mucosal cells by receptor-mediated endoycytosis where cobalamin is released, which then binds to transcobalamin