676th Meeting

Biosynthesis of cobalamin (vitamin B12)

A. I. Scott, C. A. Roessner


The biosynthesis of vitamin B12 is summarized, emphasizing the differences observed between the aerobic and anaerobic pathways. The biosynthetic route to adenosylcobalamin from its five-carbon precursor, 5-aminolaevulinic acid, can be divided into three sections: (1) the biosynthesis of uroporphyrinogen III from 5-aminolaevulinic acid, which is common to both pathways; (2) the conversion of uroporphyrinogen III into the ring-contracted, deacylated intermediate precorrin 6 or cobalt-precorrin 6, which includes the primary differences between the two pathways; and (3) the transformation of this intermediate to form adenosylcobalamin.

  • adenosylcobalamin
  • aerobic and anaerobic pathways
  • cobalt
  • precorrin 6
  • uroporphyrinogen III
  • ALA, 5-aminolaevulinic acid
  • DBI, dimethylbenzimidazole
  • NaMN, nicotinic acid mononucleotide
  • uro'gen, uroporphyrinogen