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J Bacteriol. 1980 February; 141(2): 476-484

Enzymes II of the phosphotransferase system do not catalyze sugar transport in the absence of phosphorylation.

ABSTRACT

In Salmonella typhimurium, glucose, mannose, and fructose are normally transported and phosphorylated by the phosphoenolpyruvate:sugar phosphotransferase system. We have investigated the transport of these sugars and their non-metabolizable analogs in mutant strains lacking the phospho-carrier proteins of the phosphoenolpyruvate:sugar phosphotransferase system, the enzymes I and HPr, to determine whether the sugar-specific, membrane-bound components of the phosphonenolpyruvate: sugar phosphotransferase system, the enzymes II, can catalyze the uptake of these sugars in the absence of phosphorylation. This process does not occur. We have also isolated mutant strains which lack enzyme I and HPr, but have regained the ability to grow on mannose or fructose. These mutants contained elevated levels of mannokinase (fructokinase). In addition, growth on mannose required constitutive synthesis of the galactose permease. When strains were constructed which lacked the galactose permease, they were unable to grow even on high concentrations of mannose, although elevated levels of mannokinase (fructokinase) were present. These results substantiate the conclusion that the enzymes II of the phosphoenolpyruvate:sugar phosphotransferase system are unable to carry out facilitated diffusion.

This article has been cited by other articles:

• Sutrina, S. L., Alleyne, L., Hoyte, K., Blenman, M. (2002). Effect of replacing the general energy-coupling proteins of the PEP:sugar phosphotransferase system of Salmonella typhimurium with their fructose-inducible counterparts on utilization of the PTS sugar glucitol. Microbiology 148: 3857-3864 [Abstract] [Full Text]  
• Kornberg, H. L., Lambourne, L. T. M., Sproul, A. A. (2000). Facilitated diffusion of fructose via the phosphoenolpyruvate/glucose phosphotransferase system of Escherichia coli. Proc. Natl. Acad. Sci. USA 97: 1808-1812 [Abstract] [Full Text]