Phosphotransferase systems bacteria

In this chapter, we have examined coupled transport systems that rely on ATP hydrolysis, on primary gradients of Na or Ff, and on phosphotransferase systems. Suppose you have just discovered an unusual strain of bacteria that transports rhamnose across its plasma membrane. Suggest experiments that would test whether it was linked to any of these other transport systems. 

Huebner, G. Koenig, S. Koch, M.H.J. Hengstenberg, W. Influence of Phosphoenolpyruvate and Magnesium Ions on the Quaternary Structure of Enzyme I of the Phosphotransferase System from Gram-Positive Bacteria. Biochemistry, 34, 15700-15703 (1995)... 

Romano, A. H., Trifone, J. D. and Brustolon, M. 1979. Distribution of the phosphoenolp-yruvate glucose phosphotransferase system in fermentative bacteria. J. Bacteriol 139, 93-97. 

The Permease Systems of Bacteria. The best defined of these is the galactoside permease of E. coli. This transport system mediates the active accumulation of galactosides in the presence of metabolic energy and the facilitated diffusion of these compounds when the energy system is blocked (8). A specific galactoside-binding protein has been implicated, but it seems clear that the system is different from the phosphotransferase system described above since no covalent intermediates of... 

Much of the work defining the galactoside permease systems of E. coli was done before the discovery of the ubiquitous phosphotransferases of bacteria. There is now much discussion as to the relative importance of the permease and phosphotransferase systems and on the possible re-interpretation of some of the models proposed for permease systems, because of the new information on the phosphotransferases. 

Alditols are often observed as the end-products of monosaccharide metabolism that are stored in various cellular and tissue compartments with low redox potentials. However, there are also examples of alditols as important metabolic intermediates allowing the interconversion of rare forms of certain monosaccharides. In enteric bacteria such as Escherichia coli the hexitol galactitol is taken up through enzyme II of the phosphoenol pyruvate-dependent phosphotransferase system and accumulated inside the cell as galactitol 1-phosphate. The genes involved in galactitol metabolism have been cloned on a 7.8 kb DNA fragment [201]. 

D-Fructose transport in micro-organisms, and the rapid utilization of D-fructose by bacteria is generally assumed to require the activity of a PEP (enol pyruvate phosphate)-dependent, phosphotransferase system (PTS).169 In this system, enzyme I catalyzes the transfer of phosphate from PEP to a nitrogen atom of a histidine residue in a small, high-energy protein, HPr, according to reaction I. In a subsequent step, enzyme II, in the presence of factor III, catalyzes the transfer of... 

Non-sulfur, purple, photosynthetic bacteria, Rho do spirillum rub-rum and Rhodopseudomonas spheroides172 also possess a PEP-de-pendent D-fructose phosphotransferase. Two protein fractions are required for D-fructose phosphorylation. In contrast to PEP-depend-ent, phosphotransferase systems isolated from other bacteria, the aforementioned two organisms have one active protein fraction tightly associated with the membrane fraction, while another in the crude extract is solubilized by extraction with water, and has a molecular weight of about 200,000. There is no evidence for the presence of a phosphate-carrier protein of low molecular weight like HPr.171,173 The... 

With the exception of the phosphotransferase system that is responsible for uptake of several sugars by bacteria, the active uptake of organic solutes is secondary active and coupled via cotransport to the downhill transport of a cation, Na in animal cells and H ions in microorganisms. In transcellular transport in epithelia, such as small intestine and proximal tubule of the kidney, the solutes are accumulated inside the cell via a cotransport mechanism at the luminal membrane, and leave the cell passively presumably by facilitated diffusion at the eontraluminal side. 

The biosynthetic pathway that produces bacterial cellulose from glucose and fructose is shown in Fig. 14.2. Glucose is phosphorylated by glucose hexokinase and not by the phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS). The resulting glucose-6-phosphate (G6P) is metabolized through the pentose pathway, because the activity of fructose-6-phosphate (F6P) kinase, which phos-phorylates F6P to fructose-1,6-diphosphate (FDP), is absent in acetic acid bacteria. 

Fig. 14.2 Cellulose biosynthetic pathway in cellulose-producing acetic acid bacteria. FIP firuc-tose-1-phosphate, F6P fructose-6-phosphate, FDP fructose diphosphate, PGA phosphogluconate GHK glucose hexokinase, FHK fructose hexokinase, IPFK fructose-1-phosphate kinase, FBP fructose blsphosphatase, PGI phosphoglucose isomerase, PGM phosphoglucomutase, UGP UDP-glucose pyrophosphorylase, G6PD glucose-6-phosphate dehydrogenase, PTS phosphotransferase system EMP Embden-Myerhoff pathway...

A third type of A.t. is called group translocation, because the solute is changed in the course of transport, e. g. the phosphotransferase of some bacteria, in which sugars are phosphorylated during transport. An interesting feature of this system is that phospho-e o/pyruvate rather than ATP is the phosphate donor. 

Figure 36.3 The active transport and metabolism of sugars by bacteria. PTS, membrane-associated phosphotransferase sugar-transport system PEP, phosphoenolpyruvate F , sites of fluoride inhibition...

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