OBJECTIVE To study free- and protein-bound cobalamin absorption and the correlation with atrophic gastritis in healthy middle-aged and older subjects. DESIGN A cross-sectional study. PARTICIPANTS Fifty-two healthy subjects, aged 26 to 87 years, apparently free from conditions known to influence the cobalamin status. Middle-aged subjects were defined as those younger than 65 years of age (me...

Vitamin B12 (cobalamin (Cbl)), in the cofactor forms methyl-Cbl and adenosyl-Cbl, is required for the function of the essential enzymes methionine synthase and methylmalonyl-CoA mutase, respectively. Cbl enters mammalian cells by receptor-mediated endocytosis of protein-bound Cbl followed by lysosomal export of free Cbl to the cytosol and further processing to these cofactor forms. The integral...

Dehalococcoides ethenogenes strain 195 utilizes corrinoid-containing reductive dehalogenases to reduce the environmental pollutants tetrachloroethene and trichloroethene to ethene. Although corrinoids are essential for dehalogenation activity, strain 195 cannot biosynthesize corrinoids de novo. To improve our understanding of corrinoid physiology in this bacterium, whole-genome microarrays were...

Vitamin B12 (cobalamin) is a metal complex composed of a central cobalt ion bonded to six ligands. It is essential for major biological functions such as protein, fat and carbohydrate metabolism, the maintenance of the central nervous system, and the formation of red blood cells. Since mammals cannot synthesize cobalamin, dietary intake represents the only natural source for humans. Dairy produ...

BACKGROUND Measurement of serum cobalamin levels is routinely used to diagnose cobalamin deficiency. Surprisingly, approximately 15% of patients have high cobalamin levels and no consensus exists regarding the clinical implications. METHODS Hospital-treated patients above 18 years of age referred for serum cobalamin measurement were included in groups of patients [percentage cobalamin supplem...

The metabolism of the methyl group of 5-methyltetrahydrofolate was studied in rats in which cobalamin had been inactivated by exposure to nitrous oxide and in air-breathing control animals. Methylfolate labeled with [14C] in the methyl group and with [3H] in the pteridine-PABA portion was injected and the disappearance of [14C]H3- relative to [3H]folate was measured in liver. The half-time of t...

Methylmalonic aciduria and homocystinuria, cblC type, is the most common inborn error of vitamin B(12) (cobalamin) metabolism. The recent cloning of the disease gene, MMACHC, has permitted genotype-phenotype correlation. In a 1-year-old girl, compound heterozygous c.271dupA and c.616C>T mutations in MMACHC were identified as causing an early onset methylmalonic aciduria and homocystinuria, cblC...

But very frequently among those patients, careful inquiries demonstrate that no external human intervention may explain the finding. So we have to find some explanation to the increase within the metabolism. The presence of vitamin B12 in human faeces doesn’t only correspond to what is left from the absorption in the ileum, but it also reflects the production of significant quantities of cobala...

Cobalamin neuropathy was produced in Cape fruit bats (Rousettus aegyptiacus) by a cobalamin-free diet combined with intermittent exposure to nitrous oxide, which inactivates cobalamin. Cobalamin-deficient bats had low hepatic methylmalonyl-CoA mutase holoenzyme activity, with elevated plasma and urinary methylmalonic acid levels. No significant changes could be demonstrated in the concentration...

Absorption of cobalamin free or bound to chicken serum was assessed in nine patients with pancreatic insufficiency. Simultaneously the in vitro effect of duodenal juice collected from six patients and seven controls was tested on labelled cobalamin complexed to chicken serum or to R salivary binder. Malabsorption of free cobalamin was observed in one of nine patients and in four of nine patient...