Castro, RitaBarroso, MadalenaRocha, MónicaEsse, RubenRamos, RubenRavasco, PaulaRivera, IsabelAlmeida, Isabel Tavares de2012-04-022012-04-022010Clinical Biochemistry 43(2010)645–6490009-9120http://hdl.handle.net/10451/5827doi:10.1016/j.clinbiochem.2010.01.015http://www.sciencedirect.com/science/article/pii/S0009912010000585© 2010 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.Objectives: Vitamin B12, or B12, is an essential nutrient for humans, and its deficiency is a public health problem, especially in elderly population. Around 30% of circulating total B12 levels are attached to transcobalamin II (TCN2), being referred as holotranscobalamin (holo-TC), and representing the biologically active fraction. After cellular uptake, B12 participates in the homocysteine (Hcy) metabolism. The potential influence of the described TCN2 776C> G polymorphism upon B12 intracellular delivery is a current target of research and we aimed to investigate its biochemical significance upon a healthy adult population. Design and methods: The TCN2 776C> G polymorphism was screened by PCR-RFLP in 122 individuals. Concentrations of plasma total B12, holo-TC, total Hcy and folate, as well as red blood cell folate, were determined. Results and conclusions: The studied polymorphism is common in the Portuguese population and significantly affects holo-TC but neither total B12 nor total Hcy plasma concentrations, confirming that the TCN2 776C> G genotype exerts a significant influence upon B12 cellular delivery.engTranscobalamin polymorphismVitamin B12 deliveryHomocysteinejournal article