Send to

Choose Destination
See comment in PubMed Commons below
Am J Clin Nutr. 2005 Jun;81(6):1436-41.

Transcobalamin 776C->G polymorphism negatively affects vitamin B-12 metabolism.

Author information

Food Science and Human Nutrition Department and the General Clinical Research Center, University of Florida, Gainesville, FL 32611, USA.



A common genetic polymorphism [transcobalamin (TC) 776C-->G] may affect the function of transcobalamin, the protein required for vitamin B-12 cellular uptake and metabolism. Remethylation of homocysteine is dependent on the production of 5-methyltetrahydrofolate and adequate vitamin B-12 for the methionine synthase reaction.


The objectives were to assess the influence of the TC 776C--> G polymorphism on concentrations of the transcobalamin-vitamin B-12 complex (holo-TC) and to determine the combined effects of the TC 776C-->G and methylenetetrahydrofolate reductase (MTHFR) 677C-->T polymorphisms and vitamin B-12 status on homocysteine concentrations.


Healthy, nonpregnant women (n = 359; aged 20-30 y) were screened to determine plasma vitamin B-12, serum holo-TC, and plasma homocysteine concentrations and TC 776C-->G and MTHFR 677C-->T genotypes.


The serum holo-TC concentration for women with the variant TC 776 GG genotype was significantly different (P = 0.0213) from that for subjects with the CC genotype (74 +/- 37 and 87 +/- 33 pmol/L, respectively). An inverse relation was observed between plasma homocysteine concentrations and both serum holo-TC (P </= 0.0001) and plasma vitamin B-12 (P </= 0.0001) concentrations, regardless of genotype.


These data suggest that the TC 776C-->G polymorphism negatively affects the serum holo-TC concentration and provide additional evidence that vitamin B-12 status modulates the homocysteine concentration in this population.

[Indexed for MEDLINE]
Free full text
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire
    Loading ...
    Support Center