An Escherichia coli mutant producing a truncated inactive form of GlgC synthesizes glycogen: Further evidences for the occurrence of various important sources of ADPglucose in enterobacteria

AC70R1–504 Escherichia coli mutants possess a glgC∗ gene with a nucleotide change resulting in a premature stop codon that renders a truncated, inactive form of GlgC. Cells over-expressing the wild type glgC, but not those over-expressing the AC70R1–504 glgC∗, accumulated high ADPglucose and glycogen levels. AC70R1–504 mutants accumulated glycogen, whereas ΔglgCAP deletion mutants lacking the whole glycogen biosynthetic machinery displayed a glycogen-less phenotype. AC70R1–504 cells with enhanced glycogen synthase activity accumulated high glycogen levels. By contrast, AC70R1–504 cells with high ADPG hydrolase activity accumulated low glycogen. These data further confirm that enterobacteria possess various sources of ADPglucose linked to glycogen biosynthesis.