FRUCTOSE AND MANNOSE METABOLISM IN AEROMONAS-HYDROPHILA - IDENTIFICATION OF TRANSPORT-SYSTEMS AND CATABOLIC PATHWAYS

Aeromonas hydrophila was examined for fructose and mannose transport s ystems. A. hydrophila was shown to possess a phosphoenolpyruvate (PEP) :fructose phosphotransferase system (fructose-PTS) and a mannose-speci fic PTS, both induced by fructose and mannose. The mannose-PTS of A. h ydrophila exhibited cross-reactivity with Escherichia coil mannose-PTS proteins. The fructose-PTS proteins exhibited cross-reactivities with E. coli and Xanthomonas campestris fructose-PTS proteins. In A. hydro phila grown on mannose as well as on fructose, the phosphorylated deri vative accumulated from fructose was fructose 1-phosphate. Identificat ion of fructose 1-phosphate was confirmed by C-13-NMR spectroscopy. 1- Phosphofructokinase (1-PFK), which converts the product of the PTS rea ction to fructose 1,6-diphosphate, was present in A. hydrophila grown with fructose but not on mannose. An inducible phosphofructomutase (PF M) activity, an unusual enzyme converting fructose l-phosphate to fruc tose 6-phosphate, was detected in extracts induced by mannose or fruct ose. These results suggest that in cells grown on fructose, fructose 1 -phosphate could be converted to fructose 1,6-diphosphate either direc tly by the 1-PFK activity or via fructose 6-phosphate by the PFM and 6 -phosphofructokinase activities. In cells grown on mannose, the degrad ation of fructose l-phosphate via PFM and the Embden-Meyerhof pathway appeared to be a unique route.