[Absorption, distribution and excretion of vitamin B12]

Ann Gastroenterol Hepatol (Paris). Nov-Dec 1994;30(6):270-6, 281; discussion 281-2.
[Article in French]

Abstract

During our first communication [1], the complexity of vitamin B12 digestive transport was considered. This second presentation demonstrates the route of the vitamin in the body. As cobalamin or vitamin B12 has existed for four billion years, they figure without any doubt amongst those molecules which have the most complex structure. The rarity of an architecture organised around a cobalt atom confirms their high level of originality. Their exceptional character is reflected in their cycle such as for mammals and for man where the intervention of binders, such as intrinsic factor, transcobalamin and haptocorrin is necessary for transporting them. As far as cellular metabolism is concerned, it is especially loaded sometimes with folates in the transfer of the methyl group. The molecules are spiked with hydrophobic sites. Their membrane transfer is facilitated by several types of receptors. The intestinal absorption, which appears to require the presence of two receptors and two transporters, remains for the moment a unique assimilation model. The very probable existence of an enterohepatic cycle as well as a renal reabsorption saves this molecule, itself synthesised by microorganisms only.

Publication types

  • English Abstract
  • Review

MeSH terms

  • Adult
  • Animals
  • Bacterial Outer Membrane Proteins / metabolism
  • Bile / metabolism
  • Escherichia coli Proteins*
  • Humans
  • Ileum / metabolism
  • Infant
  • Intestinal Absorption
  • Kidney / metabolism
  • Liver / metabolism
  • Membrane Transport Proteins
  • Receptors, Peptide / metabolism
  • Transcobalamins / metabolism
  • Vitamin B 12 / blood
  • Vitamin B 12 / metabolism*
  • Vitamin B 12 / urine
  • Vitamin B 12 Deficiency / metabolism

Substances

  • Bacterial Outer Membrane Proteins
  • BtuB protein, E coli
  • Escherichia coli Proteins
  • Membrane Transport Proteins
  • Receptors, Peptide
  • Transcobalamins
  • Vitamin B 12