Occurrence of more than one important source of ADPglucose linked to glycogen biosynthesis in Escherichia coli and Salmonella

To explore the possible occurrence of sources, other than GlgC, of ADPglucose linked to bacterial glycogen biosynthesis we characterized Escherichia coli and Salmonella ΔglgCAP deletion mutants lacking the whole glycogen biosynthetic machinery. These mutants displayed the expected glycogen-less phenotype but accumulated ADPglucose. Importantly, ΔglgCAP cells expressing the glycogen synthase encoding glgA gene accumulated glycogen. Protein chromatographic separation of crude extracts of ΔglgCAP mutants and subsequent activity measurement analyses revealed that these cells possess various proteins catalyzing the conversion of glucose-1-phosphate into ADPglucose. Collectively these findings show that enterobacteria possess more than one important source of ADPglucose linked to glycogen biosynthesis.