Glucose biosynthesis from three-carbon

Biosynthesis of Glucose from Three-Carbon Compounds... 

Biosynthesis of carbohydrates from carbon dioxide occurs in the stroma region of the chloroplasts via the Calvin cycle. The formation of a six-carbon sugar molecule requires six complete turns of the Calvin cycle, for each of which three ATP and two NADPH molecules are consumed. The overall biochemistry of photosynthesis for the formation of one glucose molecule from six CO2 molecules may be written as ... 

Figure 2 depicts MCL-PHA monomer supplying pathways from non-related carbon sources such as glucose. In all three pathways, monomers are derived from the fatty acid biosynthesis pathway. 

Intermediates in the biosynthetic route are 3-dehydroshikimic acid, protocate-chuic acid and catechol (Scheme 7.16). Optimization of microbial ds,ds-muconic acid synthesis required the expression of three enzymes not typically found in Escherichia coli [42cj. E. coli WNl/pWN2.248 was developed that synthesized 36.8 g of ds,ds-muconic acid in a 22% (mol/mol) yield from glucose after 48 h of culturing under fed-batch fermentor conditions. Optimization of the carbon flow directed into ds,ds-muconic acid biosynthesis and manipulation of enzyme activities were aimed at avoiding accumulation of biosynthetic intermediates. 

Thus, the three ansamycins whose biosyntheses have been investigated are derived from closely related biosynthetic pathways. The streptovaricin and rifamycin ansa chains are derived from seven propionate and two acetate (malonate) units, the geldanamycin ansa chain from four propionate, one malonate and two still unidentified 2-carbon units. In two of the three antibiotics (and presumably in streptovaricin as well) a C7N unit is derived from glucose via a shikimate-type pathway. Although a number of late intermediates in the biosynthesis of rifamycin and streptovaricins have been identified, much remains to be done. 

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