Related Experiment Video
Updated: Aug 17, 2026

Multi-Gene Single Nucleotide Polymorphism Detection in Gastric Cancer Based on Ion Semiconductor Sequencing Platform
Published on: May 10, 2024
Transcobalamin 776C->G polymorphism negatively affects vitamin B-12 metabolism
Kristina M von Castel-Dunwoody1, Gail P A Kauwell, Karla P Shelnutt
1Food Science and Human Nutrition Department and the General Clinical Research Center, University of Florida, Gainesville, FL 32611, USA.
Background:
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.
Objectives:
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.
Design:
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.
Results:
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.
Conclusions:
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.
Related Concept Videos
Vitamins
Pharmacogenetic Phenotypes: Alterations in Pharmacokinetics, Drug Targets and Biologic Milieu
Pharmacogenetics of Phase II Enzymes: N-acetyltransferase, Thiopurine S-methyltransferase, UDP-glucuronosyltransferase
Pharmacogenetics of Drug Targets: β₂-Adrenergic Receptors, Apo E, Thymidylate Synthase
Pharmacogenetics of Drug Metabolism: Overview
Factors Affecting Drug Biotransformation: Biological
Species differences: Variations in enzyme systems across species can cause disparities in drug metabolism. For instance, humans may metabolize certain drugs faster than rodents, altering therapeutic effects.
Strain differences: Genetic variations within a species can result in differing enzyme activity, impacting drug response and toxicity. For example, some mouse strains may...
