INDICATION OF A MODIFIED EMP PATHWAY FOR FRUCTOSE BREAKDOWN IN A HALOPHILIC ARCHAEBACTERIUM

The breakdown of fructose in Haloarcula (Halobacterium) vallismortis probably takes place via a novel modification of Embden Meyerhof-Parnas (EMP) pathway. Phosphorylation of fructose to yield frutose 1-phosphate as the product appears to be the initial step in fructose utilization. The noteworthy feature is that fructose 1-phosphate formation occurs by an ATP-dependent fructose 1-phosphotransferase (ketohexokinase) rather than by the phosphoenolpyruvate-dependent fructose phosphotransferase system, commonly found in eubacteria. Ketohexokinase activity has so far been known to occur only in eukaryotes. Fructose 1-phosphate was converted into fructose 1,6-biphosphate by the action of 1-phosphofructokinase. Ketohexokinase and 1-phosphofructokinase activities have been demonstrated for the first time in any archaebacterium. © 1990.