Metabolic engineering of the purine biosynthetic pathway in Corynebacterium glutamicum results in increased intracellular pool sizes of IMP and hypoxanthine.

The nucleotides IMP and GMP represent industrially relevant biotechnological products used as flavour enhancers in the food industry. The use of targeted genetic engineering for the accumulation of IMP in Corynebacterium glutamicum was investigated. Results show that blocking of IMP conversions towards AMP and GMP led to a 45-fold increase in the intracellular IMP pool to 22 μmol/g^-1_CDW. Deletion of the pgi gene encoding glucose 6-phosphate isomerase in combination with deactivation of the AMP and GMP generating reactions significantly decreased the IMP pool (13 μmol/g-1_CDW). Targeted metabolite profiling of the purine biosynthetic pathway further revealed a metabolite shift towards the formation of the corresponding nucleobase hypoxanthine (102 μmol/g-1_CDW) derived from IMP degradation. It is concluded that the purine biosynthetic pathway is strongly interconnected with various parts of central metabolism and therefore tightly controlled; however, deletion of conversions of IMP to AMP and GMP significantly increases intracellular the IMP level. Due to the complexity of this pathway further degradation from IMP to the corresponding nucleobase markedly increases suggesting additional targets for future strain optimization.