gsk disruption leads to guanosine accumulation in Escherichia coli

We tried some improvement of inosine production using an inosine-producing mutant of Escherichia coli which is deficient in purF (phosphoribosyl-pyrop hosphate (PRPP) amidotransferase gene), pm A (succinyl-adenosine 5 ' -monop hosphate (AMP) synthetase gene), deoD (purine nucleoside phosphorylase gene ), purR (purine repressor gene) and add (adenosine deaminase gene), and har boring the desensitized PRPP amidotransferase gene as a plasmid. The guaB (inosine 5 ' -monophosphate (IMP) dehydrogenase gene) disruption b rought about a slightly positive effect on the inosine productivity, Altern atively, the gsk (guanosine-inosine kinase gene) disruption caused a consid erable amount of guanosine accumulation together with a slight increase in the inosine productivity. The further addition of guaC (guanosine 5 ' -monophosphate (GMP) reductase gene) disruption did not lead to an increased guanosine accumulation, but b rought about the decrease of inosine accumulation.