METABOLISM OF TREHALOSE IN ESCHERICHIA-COLI PHYSIOLOGICAL OBSERVATIONS

The non-reducing disaccharide trehalose can be used by Escherichia coli as the only source of carbon and energy. The transport of the sugar is mediated via the phosphoenolpyruvate phosphotransferase system (PTS), and the trehalose-6-phosphate formed accross the cell membrane is further splitted by an intracellular trehalose-6-phosphate hydrolase into glucose and glucose-6-phosphate. This enzyme showed to be inducible as well as the membrane bound Enz IITre when trehalose was present in the media. PEP was the most efficient phosphate group donor, while the other phosphate group derivatives utilized were inefficient. Trehalose-6-phosphate hydrolase was catabolite repressed by 1% glucose, inhibiting its expression near 100%. Trehalase also present in the cellular extracts appeared to be a constitutive enzyme because the presence of trehalose did not affect its expression. Besides, 1% glucose only partially modified its activity level. The apparent K-m for [C-14]trehalose uptake, when cells were grown in this sugar, was 4.5 mu M, while it was 12.5 mu M when glycerol was used as the carbon source; V-max were 8 and 1 nmol/min/mg protein respectively. Preliminary experiments with Salmonella typhimurium LT2 showed that trehalase, as it was reported for E. coli by other workers and confirmed by us, is present in the periplasmic space.