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Revision as of 07:38, 1 November 2017
VITAMIN B12 METABOLICS
“Vitamin B12 deficiency is a common but serious condition...a deficiency may lead to disruption of DNA and cell metabolism and thus have serious clinical consequences.”
~Hunt Alesia et al. BMJ 2014
Clinical and health consequences of vitamin B12 deficiency, adapted from Hunt Alesia et al. BMJ 2014.
The Vitamin B12 Dilemma
- Most cyanobacteria, including S. elongatus PCC 7942 and A. platensis, produce vitamin B12 analogs, which are forms of vitamin B12 that is inactive in mammals[10,11].
- Vitamin DMB B12 is crucial for nucleotide synthesis, methionine synthesis, nervous system function, neurodevelopment, and metabolism of folate, branched amino acids, and odd-chain fatty acids in humans[12,16,19].
- Vitamin DMB B12 proves to be a leading global vitamin deficiency and one of the most difficult vitamins to naturally consume [15].
- Vitamin B12 deficiency can lead to a wide array of symptoms and diseases.
Vitamin B12 (a) structure composed of Cobalmin with a corrin ring and centralized cobalt (1) and a lower ligand, which can be constructed from DMB (2) or adenine (3) [12].
What makes Vitamin B12 active?
- Vitamin B12 is composed of a corrin ring, centralized cobalt, and covalently bound upper and lower axial ligands[12,18].
- For vitamin B12 to be active in mammals, the lower ligand must be constructed with 5,6-dimethylbenzimidazole and α-ribosole-5-phosphate[12].
- Without these two compounds, the cell cannot synthesize the 5,6-dimethylbenzimidazolyl nucleotide moiety (5,6-DMB) de novo and instead uses cellular adenine as the lower ligand, creating pseudo-B12[11,12].
- 5,6-DMB, as a lower ligand, binds the glycoprotein intrinsic factor to cobalamin, which aids in transport of the B12 molecule within the mammalian gastrointestinal tract[12].
- Without the glycoprotein intrinsic factor, vitamin B12 cannot be absorbed[16].
How Active Vitamin B12 iIs Synthesized
Vitamin DMB B12 synthesis follows the pathway map above, adapted from Metacyc; the pink genes are absent in S. elongatus PCC 7942
Our Mechanism of Action
- The genes ssuE and bluB are absent in S. elongatus PCC 7942.
- In order to induce the synthesis of DMB B12 in S. elongatus PCC 7942, these previously absent genes must be artificially integrated into the organism’s genome.
- The insertion of these genes will allow 5,6-DMB to be synthesized within the host.
- S. elongatus PCC 7942 has the necessary genes (cobU, pgam3, IdiB, cobS) to complete the synthesis of vitamin B12 using 5,6-DMB as the lower ligand.
- The result: intracellular production of vitamin DMB B12 within S. elongatus PCC 7942.