Using comparative analysis of genes, operons, and regulatory elements, we describe the cobalamin (vitamin B12) biosynthetic pathway in available prokaryotic genomes. Here we found a highly conserved RNA secondary structure, the regulatory B12 element, which is widely distributed in the upstream regions of cobalamin biosynthetic/transport genes in eubacteria. In addition, the binding signal (CBL...

BtuCD-F is an ABC transporter that mediates cobalamin uptake into Escherichia coli. Early in vivo data suggested that BtuCD-F might also be involved in the uptake of cobinamide, a cobalamin precursor. However, neither was it demonstrated that BtuCD-F indeed transports cobinamide, nor was the structural basis of its recognition known. We synthesized radiolabeled cyano-cobinamide and demonstrated...

Vegetarians are at risk to develop deficiencies of some essential nutrients, especially vitamin B-12 (cobalamin). Cobalamin occurs in substantial amounts only in foods derived from animals and is essential for one-carbon metabolism and cell division. Low nutritional intake of vitamin B-12 may lead to negative balance and, finally, to functional deficiency when tissue stores of vitamin B-12 are ...

BACKGROUND Haptocorrin (HC) carries the major part of circulating cobalamin, but whether HC is altered on treatment with vitamin B12 remains unknown. METHODS Our study included 3 populations: a population of vegan men (n = 174; vegan population), of whom 63 were treated daily with 5 mg of oral vitamin B12 for 3 months; a group of patients with a previous methylmalonic acid (MMA) concentration...

OBJECTIVE Recent studies have shown an increase of mild serum cobalamin (vitamin B(12)) deficiency in some Latin American countries; however, no data are available from Costa Rica. The purpose of this work was to establish the prevalence of serum vitamin B(12) deficiency among Costa Rican young adults and to study some factors that may help explain the serum cobalamin concentrations. METHODS ...

Studies comparing the binding of genuine cobalamin (vitamin B12) to that of its natural or synthetic analogues have long established increasing ligand specificity in the order haptocorrin, transcobalamin and intrinsic factor, the high-affinity binding proteins involved in cobalamin transport in mammals. In the present study, ligand specificity was investigated from a structural point of view, f...

Cobalamin deficiency is relatively common, but the great majority of cases in epidemiologic surveys have subclinical cobalamin deficiency (SCCD), not classical clinical deficiency. Because SCCD has no known clinical expression, its diagnosis depends solely on biochemical biomarkers, whose optimal application becomes crucial yet remains unsettled. This review critically examines the current diag...

B(12)-dependent methionine synthase (MetH) from Escherichia coli is a large modular protein that is alternately methylated by methyltetrahydrofolate to form methylcobalamin and demethylated by homocysteine to form cob(I)alamin. Major domain rearrangements are required to allow cobalamin to react with three different substrates: homocysteine, methyltetrahydrofolate, and S-adenosyl-l-methionine (...

OBJECTIVE To assess the long term outcome of patients with methylmalonic acidaemia in a cross sectional study. PATIENTS All 35 patients with methylmalonic acidaemia seen at Great Ormond Street Hospital for Children in London, UK between 1970 and 1996 were studied. They were divided into cobalamin responsive (n = 6) and non-responsive (n = 29), and early and late onset groups. RESULTS There ...

BACKGROUND We examined the effect of oral vitamin B(12) treatment on fluctuations in plasma total cobalamin and its binding proteins transcobalamin (TC) and haptocorrin (HC). METHODS Patients (n = 88; age range, 38-80 years) undergoing coronary angiography (part of the homocysteine-lowering Western Norway B-Vitamin Intervention Trial) were allocated to daily oral treatment with (a) vitamin B(...