Expression of the guanosine-inosine kinase gene from Exiguobacterium acetylicum in Corynebacterium ammoniagenes and phosphorylation of inosine to produce inosine 5′-monophosphate

Abstract

The guanosine-inosine kinase gene (gsk) isolated from Exiguobacterium acetylicum was expressed in an ATP-regenerating strain, Corynebacterium ammoniagenes. In order to induce its expression, three promoters (those for the Escherichia coli tac, Escherichia coli trp, and Corynebacterium glutamicum odhA gene) with the corresponding ribosome-binding sequences were examined. The E. coli trp promoter was most efficient with regard to inducing the expression of gsk in C. ammoniagenes. Further, the resulting strain, which has both inosine kinase activity and ATP-regenerating activity, was used to induce the phosphorylation of inosine to produce inosine 5′-monophosphate (5′-IMP), which is widely used as a flavor enhancer; approximately 80 g of 5′-IMP/l was produced with a molar conversion ratio of 80%.