Team:UCSC/B-12



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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


  1. Most cyanobacteria, including S. elongatus PCC 7942 and A. platensis, produce vitamin B12 analogs, which are forms of vitamin B12 that mammals cannot absorb[10,11].

  2. Vitamin DMB B12, which is the only form of vitamin B12 that mammals can absorb, 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].

  3. Vitamin DMB B12 proves to be a leading global vitamin deficiency and one of the most difficult vitamins to naturally consume [15].

  4. 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?


  1. Vitamin B12 is composed of a corrin ring, centralized cobalt, and covalently bound upper and lower axial ligands[12,18].

  2. For vitamin B12 to be active in mammals, the lower ligand must be constructed with 5,6-dimethylbenzimidazole and α-ribosole-5-phosphate[12] effectively creating vitamin DMB B12.

  3. 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 B12 analogs[11,12].

  4. 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].

  5. Without the glycoprotein intrinsic factor, vitamin B12 cannot be absorbed[16].



How Vitamin DMB B12 Is 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


  1. The genes ssuE and bluB are absent in S. elongatus PCC 7942.

  2. 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.

  3. The insertion of these genes will allow 5,6-DMB to be synthesized within the host.

  4. 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.

  5. The result: intracellular production of vitamin DMB B12 within S. elongatus PCC 7942.






P R O J E C T

HOMEPAGE

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ACETAMINOPHEN
MODELING
RESULTS
TARGET ORGANISM
PARTS
  • [10] K. E. Helliwell, A. D. Lawrence, A. Holzer, U. J. Kudahl, S. Sasso, B. Kr ̈autler, D. J. Scanlan, M. J. Warren, and A. G. Smith, “Cyanobacteria and Eukaryotic Algae Use Different Chemical Variants of Vitamin B12,” Current biology: CB, vol. 26, pp. 999–1008, Apr. 2016.
  • [11] V. Karuppiah, W. Sun, and Z. Li, “Natural Products of Actinobacteria Derived from Marine Organisms,” in Studies in Natural Products Chemistry, vol. 48, pp. 417-446, Elsevier, 2016. DOI: 10.1016/B978-0-444-63602-7.00013-8.
  • [12] P. Deptula, P. Kylli, B. Chamlagain, L. Holm, R. Kostiainen, V. Piironen, K. Savijoki, and P. Varmanen, “BluB/CobT2 fusion enzyme activity reveals mechanisms responsible for production of active form of vitamin B12 by Propionibacterium freudenreichii,” Microbial Cell Factories, vol. 14, p. 186, Nov. 2015.
  • [13] D. L. R. Narasimha, G. S. Venkataraman, S. K. Duggal, and B. O. Eggum, “Nutritional quality of the blue-green alga Spirulina platensis geitler,” Journal of the Science of Food and Agriculture, vol. 33, pp. 456{460, May 1982.
  • [14] M. Fenech, “Folate (vitamin B9) and vitamin B12 and their function in the maintenance of nuclear and mitochondrial genome integrity,” Mutation Research, vol. 733, pp. 21-33, May 2012.
  • [15] B. Hemmer, F. X. Glocker, M. Schumacher, G. Deuschl, and C. H. Lucking, “Subacute combined degeneration: clinical, electrophysiological, and magnetic resonance imaging findings,” Journal of Neurology, Neurosurgery, and Psychiatry, vol. 65, pp. 822-827, Dec. 1998.
  • [16] S. P. Stabler, “Vitamin B12 Deficiency,” New England Journal of Medicine, vol. 368, pp. 149-160, Jan. 2013.
  • [17] M. T. Steen, A. M. Boddie, A. J. Fisher, W. Macmahon, D. Saxe, K. M. Sullivan, P. P. Dembure, and L. J. Elsas, “Neural-tube defects are associated with low concentrations of cobalamin (vitamin B12) in amniotic fluid,” Prenatal Diagnosis, vol. 18, pp. 545-555, June 1998.
  • [18] S. A. Newmister, C. H. Chan, J. C. Escalante-Semerena, and I. Rayment, “Structural Insights into the Function of the Nicotinate Mononucleotide:phenol/p-cresol Phosphoribosyltransferase (ArsAB) Enzyme from Sporomusa ovata,” Biochemistry, vol. 51, pp. 8571–8582, Oct. 2012.
  • [19] Hunt Alesia, Harrington Dominic, Robinson Susan. Vitamin B12 deficiency BMJ 2014; 349 :g5226.


    • S P O N S O R S
    S O C I A L
    C O N T A C T
    Jack Baskin School of Engineering
    University of California, Santa Cruz
    1156 High Street
    Santa Cruz, California, 95064