Phosphotransferase‐dependent glucose transport in Corynebacterium glutamicum

Abstract

G.M. MALIN AND G.I. BOURD. 1991. The transport system for glucose and its non‐metabolizable analogue methyl‐α‐D‐glucoside (MG) has been described in Corynebacterium glutamicum. The initial product of the transport reaction was shown to be a phosphate ester of MG (MGP). Free MG appeared inside the cells as a result of MGP dephosphorylation. The bacteria transported MG with an apparent Km of 0.08 ± 0.017 mmol/l and Vmax of 21 ± 2.3 nmol/(min × mg dry wt). Toluenized cells and crude cell extracts catalysed phosphoenolpyruvate (PEP)‐dependent phosphorylation of MG and glucose. Both the membrane and the cytoplasmic fractions of bacterial extracts were required for phosphotransferase reaction. Most of the spontaneous mutants resistant to 2‐deoxyglucose (DG), xylitol and 5‐thioglucose were defective both in transport and in PEP‐dependent phosphorylation of MG. Some strains were defective only in glucose utilization and some were also unable to grow on a number of other sugars. The phosphotransferase activity in extracts from mutant cells was restored by the addition of either membrane or cytoplasmic fraction from wild type bacteria. It was concluded that Corynebacterium glutamicum accumulated glucose and MG by means of a PEP‐dependent phosphotransferase system (PTS).