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Cobalamin

Cobalt-containing corrinoid vitamin (B12) that, as methylcobalamin and adenosylcobalamin, serves as cofactor for methionine synthase (cytoplasm) and methylmalonyl-CoA mutase (mitochondria).

Also: Vitamin B12

Cobalamin absorption requires gastric acid and pepsin (for protein release), intrinsic factor (IF) secreted by parietal cells, and ileal cubam (cubilin/amnionless) receptor. Pernicious anemia is autoimmune destruction of parietal cells with loss of IF. Deficiency causes megaloblastic anemia, hyperhomocysteinemia, elevated methylmalonic acid, and subacute combined degeneration of the spinal cord. Older adults frequently have food-bound B12 malabsorption from atrophic gastritis, addressable with crystalline B12 from supplements or fortified foods.

How one textbook covers it

  • Modern Nutrition in Health and Disease, 12th ed. — Ch 28: Cobalamin (Vitamin B12)

    Cobalamin absorption requires gastric acid and pepsin (for protein release), intrinsic factor (IF) secreted by parietal cells, and ileal cubam (cubilin/amnionless) receptor. Pernicious anemia is autoimmune destruction of parietal cells with loss of IF. Deficiency causes megaloblastic anemia, hyperhomocysteinemia, elevated methylmalonic acid, and subacute combined degeneration of the spinal cord. Older adults frequently have food-bound B12 malabsorption from atrophic gastritis, addressable with crystalline B12 from supplements or fortified foods.

Related terms

Folate, Intrinsic factor, Methylmalonic acid, Pernicious anemia