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Team:Edinburgh/Plan/StarchSynthesis
From 2008.igem.org
Contents |
Starch synthesis
Glucose must be taken up by the cells and synthesised first into glycogen and then starch.
2. Starch synthesis
The second phase is the conversion of glycogen to starch. To achieve this we are creating isoamylase and granule-bound starch synthesase BioBricks (isa1, isa2 and gbss) from Zea mays cDNAs. These three genes together should be sufficient for the production of starch from glycogen.
Cellulases must be synthesised and must be released into the growth medium, where they can digest cellulose into starch.
Genes
Glycogen synthesis
E. coli and B. subtilis are natively able to synthesise glycogen from starch (see Figure 1 for E. coli's native pathway). However, we want to upregulate this pathway. The gene glgC (ADP-glucose pyrophosphorylase, catalysing the convertion glucose 1-phosphate and ATP to ADP-glucose and PPi) is responsible for the most rate-limiting step of glycogen synthesis in E. coli. This is because the protein is negatively regulated by 5'-AMP, ADP or orthophosphate. The glgC16 mutant has the substitution G336D to glgC, and has been reported to increase the yield of glycogen. This is due in part to the loss of allosteric inhibition and is also due to increased activity in the absence of its activator molecule, fructose 1,6 bis-phosphate.
