A temperature-sensitive Mycobacterium smegmatis glgE mutation leads to a loss of GlgE enzyme activity and thermostability and the accumulation of ?-maltose-1-phosphate

The bacterial GlgE pathway is the third known route to glycogen and only one present in mycobacteria. It contributes virulence of Mycobacterium tuberculosis . involvement biosynthesis was discovered twenty years ago when phenotype a temperature-sensitive smegmatis mutation rescued by glgE gene. evidence at time suggested coded for glucanase responsible hydrolysis glycogen, stark contrast with recent showing be polymerase its biosynthesis. We reconstructed examined mutant characterised mutated enzyme. strain accumulated substrate GlgE, ?-maltose-1-phosphate, non-permissive temperature. assay used original study shown give false positive result ?-maltose-1-phosphate. accumulation ?-maltose-1-phosphate due lowering k cat as well loss stability 42 °C. reported rescue GarA could potentially involve an interaction but none detected. have been able reconcile apparently contradictory observations shed light on basis mutation. This highlights how flux through can slow growth • A single amino acid substitution leads activity stability. Temperature-sensitivity GlgE's vivo. Reduced attributed this substrate. reconciles published previously.