PEP-dependent Phosphotransferase System Research Articles

Transporters of glucose and other carbohydrates in bacteria.

Glucose arguably is the most important energy carrier, carbon source for metabolites and building block for biopolymers in all kingdoms of life. The proper function of animal organs and tissues depends on the continuous supply of glucose from the bloodstream. Most animals can resorb only a small number of monosaccharides, mostly glucose, galactose and fructose, while all other sugars oligosaccharides and dietary fibers are degraded and metabolized by the microbiota of the lower intestine. Bacteria, in contrast, are omnivorous. They can import and metabolize structurally different sugars and, as a consortium of different species, utilize almost any sugar, sugar derivative and oligosaccharide occurring in nature. Bacteria have membrane transport systems for the uptake of sugars against steep concentration gradients energized by ATP, the proton motive force and the high energy glycolytic intermediate phosphoenolpyruvate (PEP). Different uptake mechanisms and the broad range of overlapping substrate specificities allow bacteria to quickly adapt to and colonize changing environments. Here, we review the structures and mechanisms of bacterial representatives of (i) ATP-dependent cassette (ABC) transporters, (ii) major facilitator (MFS) superfamily proton symporters, (iii) sodium solute symporters (SSS) and (iv) enzyme II integral membrane subunits of the bacterial PEP-dependent phosphotransferase system (PTS). We give a short overview on the distribution of transporter genes and their phylogenetic relationship in different bacterial species. Some sugar transporters are hijacked for import of bacteriophage DNA and antibacterial toxins (bacteriocins) and they facilitate the penetration of polar antibiotics. Finally, we describe how the expression and activity of certain sugar transporters are controlled in response to the availability of sugars and how the presence and uptake of sugars may affect pathogenicity and host-microbiota interactions.

Investigating the strategies for microbial production of trehalose from lignocellulosic sugars.

Trehalose, a multi-functional and value-added disaccharide, can be efficiently biosynthesized from glucose by using a synergetic carbon utilization mechanism (SynCar) which coupled phosphoenolpyruvate (PEP) generation from the second carbon source with PEP-dependent phosphotransferase system (PTS) to promote non-catabolic use of glucose. Considering glucose and xylose present in large amounts in lignocellulosic sugars, we explored new strategies for conversion of both sugars into trehalose. Herein, we first attempted trehalose production from xylose directly, based on which, synergetic utilization of glucose, and xylose prompted by SynCar was implemented in engineered Escherichia coli. As the results, the final titer of trehalose reached 5.55 g/L in shake flask experiments. The conversion ratio or utilization efficiency of glucose or xylose to trehalose was around fourfold higher than that of the original strain (YW-3). This work not only demonstrated the possibility of directly converting xylose (C5 sugar) into trehalose (C12 disaccharide), but also suggested a promising strategy for trehalose production from lignocellulosic sugars for the first time.

Identification of a glucose-mannose phosphotransferase system in Clostridium beijerinckii.

Effective uptake of fermentable substrates is a fundamentally important aspect of any fermentation process. The solventogenic bacterium Clostridium beijerinckii is noted for its ability to ferment a wide range of carbohydrates, yet few of its sugar transport systems have been characterized. In common with other anaerobes, C. beijerinckii shows a marked dependence on the PEP-dependent phosphotransferase system (PTS) for sugar accumulation. In this study, the gene cbe0751 encoding the sugar-specific domains of a phosphotransferase belonging to the glucose family was cloned into an Escherichia coli strain lacking the ability to take up and phosphorylate glucose. Transformants gained ability to ferment glucose, and also mannose, and further analysis of a selected transformant demonstrated that it could take up and phosphorylate glucose, confirming that cbe0751 encodes a glucose PTS which also recognizes mannose as a substrate. RT-PCR analysis showed that cbe0751 was expressed in cultures grown on both substrates, but also to varying extents during growth on some other carbon sources. Although analogue inhibition studies suggested that Cbe0751 is not the only glucose PTS in C. beijerinckii, this system should nevertheless be regarded as a potential target for metabolic engineering to generate a strain showing improved sugar fermentation properties.

Sugar uptake by the solventogenic clostridia.

The acetone–butanol–ethanol fermentation of solventogenic clostridia was operated as a successful, worldwide industrial process during the first half of the twentieth century, but went into decline for economic reasons. The recent resurgence in interest in the fermentation has been due principally to the recognised potential of butanol as a biofuel, and development of reliable molecular tools has encouraged realistic prospects of bacterial strains being engineered to optimise fermentation performance. In order to minimise costs, emphasis is being placed on waste feedstock streams containing a range of fermentable carbohydrates. It is therefore important to develop a detailed understanding of the mechanisms of carbohydrate uptake so that effective engineering strategies can be identified. This review surveys present knowledge of sugar uptake and its control in solventogenic clostridia. The major mechanism of sugar uptake is the PEP-dependent phosphotransferase system (PTS), which both transports and phosphorylates its sugar substrates and plays a central role in metabolic regulation. Clostridial genome sequences have indicated the presence of numerous phosphotransferase systems for uptake of hexose sugars, hexose derivatives and disaccharides. On the other hand, uptake of sugars such as pentoses occurs via non-PTS mechanisms. Progress in characterization of clostridial sugar transporters and manipulation of control mechanisms to optimise sugar fermentation is described.

Improvement of L-phenylalanine production from glycerol by recombinant Escherichia coli strains: the role of extra copies of glpK, glpX, and tktA genes.

BackgroundFor the production of L-phenylalanine (L-Phe), two molecules of phosphoenolpyruvate (PEP) and one molecule erythrose-4-phosphate (E4P) are necessary. PEP stems from glycolysis whereas E4P is formed in the pentose phosphate pathway (PPP). Glucose, commonly used for L-Phe production with recombinant E. coli, is taken up via the PEP-dependent phosphotransferase system which delivers glucose-6-phosphate (G6P). G6P enters either glycolysis or the PPP. In contrast, glycerol is phosphorylated by an ATP-dependent glycerol kinase (GlpK) thus saving one PEP. However, two gluconeogenic reactions (fructose-1,6-bisphosphate aldolase, fructose-1,6-bisphosphatase, FBPase) are necessary for growth and provision of E4P. Glycerol has become an important carbon source for biotechnology and reports on production of L-Phe from glycerol are available. However, the influence of FBPase and transketolase reactions on L-Phe production has not been reported.ResultsL-Phe productivity of parent strain FUS4/pF81 (plasmid-encoded genes for aroF, aroB, aroL, pheA) was compared on glucose and glycerol as C sources. On glucose, a maximal carbon recovery of 0.19 mM CPhe/CGlucose and a maximal space-time-yield (STY) of 0.13 g l−1 h−1 was found. With glycerol, the maximal carbon recovery was nearly the same (0.18 mM CPhe/CGlycerol), but the maximal STY was higher (0.21 g l−1 h−1). We raised the chromosomal gene copy number of the genes glpK (encoding glycerol kinase), tktA (encoding transketolase), and glpX (encoding fructose-1,6-bisphosphatase) individually. Overexpression of glpK (or its feedback-resistant variant, glpKG232D) had little effect on growth rate; L-Phe production was about 30% lower than in FUS4/pF81. Whereas the overexpression of either glpX or tktA had minor effects on productivity (0.20 mM CPhe/CGlycerol; 0.25 g l−1 h−1 and 0.21 mM CPhe/CGlycerol; 0.23 g l−1 h−1, respectively), the combination of extra genes of glpX and tktA together led to an increase in maximal STY of about 80% (0.37 g l−1 h−1) and a carbon recovery of 0.26 mM CPhe/CGlycerol.ConclusionsEnhancing the gene copy numbers for glpX and tktA increased L-Phe productivity from glycerol without affecting growth rate. Engineering of glycerol metabolism towards L-Phe production in E. coli has to balance the pathways of gluconeogenesis, glycolysis, and PPP to improve the supply of the precursors, PEP and E4P.

A role for EIIANtr in controlling fluxes in the central metabolism of E. coli K12

To investigate a possible role of the nitrogen-PTS (PTSNtr) in controlling carbon metabolism, we determined the growth of Escherichia coli LJ110 and of isogenic derivatives, mutated in components of the PTSNtr, on different carbon sources. The PTSNtr is a set of proteins homologous to the PEP-dependent phosphotransferase system (C-PTS) that transfers a phosphate group from PEP over EINtr (encoded by ptsP) and NPr (encoded by ptsO) to EIIANtr (encoded by ptsN). Strains deleted in ptsN were characterized by a high acetate production coupled to slow growth on glycolytic substrates. The ΔptsP and the ΔptsO strain showed the same behavior as the parent strain. As the phosphorylation level of EIIANtr in these mutants differed significantly from that of the parent strain, phosphorylation of EIIANtr obviously is not important for its function. During growth in minimal medium with defined carbon sources, EIIANtr was always completely phosphorylated in LJ110. Significant amounts of dephosphorylated EIIANtr were only visible in strains lacking EINtr or NPr. mRNA expression studies on glucose revealed a downregulation of genes encoding TCA cycle enzymes when EIIANtr was absent. 13C-flux analyses confirmed higher fluxes towards acetate and lower fluxes in the TCA cycle in the ptsN mutants but additionally hinted to a slightly but significantly increased flux through the pyruvate dehydrogenase complex (PDH). During growth on succinate the ΔptsN strain accumulated mutations in rpoS, while no rpoS mutants were observed for the ΔptsN-O strain. This hints to an additional function of NPr during growth with succinate.

Precise excision of Tn5 in Escherichia coli K12 mutants with alterations in common component of phosphotransferase system and in DNA-gyrase subunits

The effect of ptsH, gyrA and gyrB mutations on the frequency of precise excision (PE) of transposon Tn5 was studied in Escherichia coli K12. The conjugative plasmid with Tn5 integrated in the tet gene of Tn10 was used as a model in the experiments. It was shown that mutational damage to the HPr protein (ptsH mutation), a common component of the bacterial PEP-dependent phosphotransferase system (PTS), or changes in the DNA-gyrase A subunit (gyrA mutation) increased the frequency of PE. The gyrB mutation (mutational damage of DNA-gyrase B subunit) had almost no influence on PE frequency. The presence of glucose or fructose in growth media resulted in enhanced PE frequency, while the insertion of ptsH or gyrA mutations under the same conditions caused a decrease in the PE frequency. gyrB mutants had no similar effects. The demonstrated data indicate the need for the intact PTS for the balanced supercoiled DNA state maintained by DNA gyrase.

Metabolic evolution of energy-conserving pathways for succinate production in Escherichia coli

During metabolic evolution to improve succinate production in Escherichia coli strains, significant changes in cellular metabolism were acquired that increased energy efficiency in two respects. The energy-conserving phosphoenolpyruvate (PEP) carboxykinase (pck), which normally functions in the reverse direction (gluconeogenesis; glucose repressed) during the oxidative metabolism of organic acids, evolved to become the major carboxylation pathway for succinate production. Both PCK enzyme activity and gene expression levels increased significantly in two stages because of several mutations during the metabolic evolution process. High-level expression of this enzyme-dominated CO(2) fixation and increased ATP yield (1 ATP per oxaloacetate). In addition, the native PEP-dependent phosphotransferase system for glucose uptake was inactivated by a mutation in ptsI. This glucose transport function was replaced by increased expression of the GalP permease (galP) and glucokinase (glk). Results of deleting individual transport genes confirmed that GalP served as the dominant glucose transporter in evolved strains. Using this alternative transport system would increase the pool of PEP available for redox balance. This change would also increase energy efficiency by eliminating the need to produce additional PEP from pyruvate, a reaction that requires two ATP equivalents. Together, these changes converted the wild-type E. coli fermentation pathway for succinate into a functional equivalent of the native pathway that nature evolved in succinate-producing rumen bacteria.

Inhibitory effect of phosphoenolpyruvate on glycolytic enzymes in Escherichia coli

For analyzing the control of energy metabolism in Escherichia coli, we carried out kinetic analyses of glycolytic enzymes purified from the overexpressing clones of E. coli K12 W3110 that were constructed with the vector pCA24N. Phosphoenolpyruvate (PEP) acted as an effective inhibitor of enzymes of the preparatory phase in glycolysis. Glucokinase was potently inhibited by PEP in a competitive manner with respect to ATP: the K i value for PEP was 0.1 mM. PEP further inhibited phosphoglucoisomerase to a lesser extent, and phosphofructokinase A and aldolase A with 10-fold the K i values of glucokinase and phosphoglucoisomerase. Glucose is incorporated into E. coli through two pathways: the PTS (PEP-dependent phosphotransferase system) and the glucokinase reaction. PEP, a potent inhibitor of E. coli glucokinase, unlike most eukaryotic hexokinases, can act as a signal molecule controlling glucose uptake and glycolytic flux in cells.

Enzymatic Synthesis of Cytidine 5′-Monophospho-N-acetylneuraminic Acid

We have established an efficient method for enzymatic production of cytidine 5'-monophospho-N-acetylneuraminic acid (CMP-NeuAc) from inexpensive materials, N-acetylglucosamine (GlcNAc) and cytidine 5'-monophosphate (CMP). The Haemophilus influenzae nanE gene encoding GlcNAc 6-phosphate (GlcNAc 6-P) 2-epimerase and the Campylobacter jejuni neuB1 gene encoding N-acetylneuraminic acid (NeuAc) synthetase, both of whose products are involved in NeuAc biosynthesis, were cloned and co-expressed in Escherichia coli cells. We examined the synthesis of NeuAc from GlcNAc via GlcNAc 6-P, N-acetylmannosamine (ManNAc) 6-P, and ManNAc by the use of E. coli cells producing GlcNAc 6-P 2-epimerase and NeuAc synthetase, in expectation of biological functions of E. coli such as the supply of phosphoenolpyruvate (PEP), which is an essential substrate for NeuAc synthetase, GlcNAc phospholylation by the PEP-dependent phosphotransferase system, and dephospholylation of ManNAc 6-P. Eleven mM NeuAc was synthesized from 50 mM GlcNAc by recombinant E. coli cells with the addition of glucose as an energy source. Next we attempted to synthesize CMP-NeuAc from GlcNAc and CMP using yeast cells, recombinant E. coli cells, and H. influenzae CMP-NeuAc synthetase, and succeeded in efficient production of CMP-NeuAc due to a sufficient supply of PEP and efficient conversion of CMP to cytidine 5'-triphosphate by yeast cells.

Glucose uptake by Listeria monocytogenes Scott A and inhibition by pediocin JD.

Glucose uptake by Listeria monocytogenes Scott A was inhibited by the bacteriocin pediocin JD and by the protonophore carbonyl cyanide m-chlorophenyhydrazone. Experiments with monensin, nigericin, chlorhexidine diacetate, dinitrophenol, and gramicidin, however, showed that glucose uptake could occur in the absence of a proton motive force. L. monocytogenes cell extracts phosphorylated glucose when phosphoenolpyruvate (PEP) was present in the assay mixture, and whole cells incubated with 2-deoxyglucose accumulated 2-deoxyglucose-6-phosphate, indicating the presence of a PEP-dependent phosphotransferase system in this organism. Glucose phosphorylation also occurred when ATP was present, suggesting that a proton motive force-mediated glucose transport system may also be present. We conclude that L. monocytogenes Scott A accumulates glucose by phosphotransferase and proton motive force-mediated systems, both of which are sensitive to pediocin JD.

Effect of growth conditions on the Streptococcus bovis phosphoenolpyruvate glucose phosphotransferase system1

Four strains of the ruminal bacterium Streptococcus bovis were surveyed for phosphoenolpyruvate (PEP) and ATP-dependent phosphorylation of glucose and the nonmetabolizable glucose analog 2-deoxyglucose. All four strains had high rates of glucose phosphorylation with either phosphoryl donor, but 2-deoxyglucose activity was much higher in the presence of PEP. These results provide evidence for a PEP-dependent glucose phosphotransferase system in these bacteria. Mannose and 2-deoxyglucose inhibited PEP-dependent phosphorylation of glucose by S. bovis JB1 by 50 and 38%, respectively, whereas alpha-methylglucoside had little effect. Mannose was a competitive inhibitor of PEP-dependent phosphorylation of glucose with an inhibition constant of 2.8 mM, and PEP-dependent activity in cells grown in batch culture was optimal at pH 7.2. When S. bovis JB1 was grown in continuous culture, PEP-dependent phosphorylation of glucose and 2-deoxyglucose was highest in cells grown at a dilution rate of .10/h and at low glucose concentrations. Phosphoenolpyruvate-dependent activity was optimum at a growth pH of 5.0 for cells grown in medium that contained less than 6.0 g/liter of glucose. These data indicate that PEP-dependent glucose phosphotransferase system activity can be influenced depending on the growth conditions used to culture S. bovis. Furthermore, these results suggest that environmental conditions within the rumen will affect how glucose is transported by S. bovis.

Phosphotransferase‐dependent glucose transport in Corynebacterium glutamicum

G.M. MALIN AND G.I. BOURD. 1991. The transport system for glucose and its non‐metabolizable analogue methyl‐α‐D‐glucoside (MG) has been described in Corynebacterium glutamicum. The initial product of the transport reaction was shown to be a phosphate ester of MG (MGP). Free MG appeared inside the cells as a result of MGP dephosphorylation. The bacteria transported MG with an apparent Km of 0.08 ± 0.017 mmol/l and Vmax of 21 ± 2.3 nmol/(min × mg dry wt). Toluenized cells and crude cell extracts catalysed phosphoenolpyruvate (PEP)‐dependent phosphorylation of MG and glucose. Both the membrane and the cytoplasmic fractions of bacterial extracts were required for phosphotransferase reaction. Most of the spontaneous mutants resistant to 2‐deoxyglucose (DG), xylitol and 5‐thioglucose were defective both in transport and in PEP‐dependent phosphorylation of MG. Some strains were defective only in glucose utilization and some were also unable to grow on a number of other sugars. The phosphotransferase activity in extracts from mutant cells was restored by the addition of either membrane or cytoplasmic fraction from wild type bacteria. It was concluded that Corynebacterium glutamicum accumulated glucose and MG by means of a PEP‐dependent phosphotransferase system (PTS).

Biochemical Mechanisms of Enhanced Inhibition of Fluoride on the Anaerobic Sugar Metabolism by Streptococcus sanguis

The effect of fluoride on acid production by Streptococcus sanguis ATCC 10556 was compared under anaerobic and aerobic conditions. The rate of acid production under constant-pH and pH-free-fall conditions was determined during glucose metabolism by resting cells. Anaerobic glycolysis was inhibited more strongly by fluoride than was aerobic glycolysis. Intracellular levels of 3-phosphoglyceric, 2-phosphoglyceric, and phosphoenolpyruvic acids were lower under anaerobic conditions than under aerobic conditions. Thus, S. sanguis had a low phosphoenolpyruvate (PEP) potential under anaerobic conditions. This low PEP potential was suggested to account for the more effective fluoride inhibition of enolase and, consequently, the reduced transport of sugar by the PEP-dependent phosphotransferase system of this micro-organism.

Characterization and nucleotide sequence of the cryptic cel operon of Escherichia coli K12.

Wild-type Escherichia coli are not able to utilize beta-glucoside sugars because the genes for utilization of these sugars are cryptic. Spontaneous mutations in the cel operon allow its expression and enable the organism to ferment cellobiose, arbutin and salicin. In this report we describe the structure and nucleotide sequence of the cel operon. The cel operon consists of five genes: celA, whose function is unknown; celB and celC which encode phosphoenolpyruvate-dependent phosphotransferase system enzyme IIcel and enzyme IIIcel, respectively, for the transport and phosphorylation of beta-glucoside sugars; celD, which encodes a negative regulatory protein; and celF, which encodes a phospho-beta-glucosidase that acts on phosphorylated cellobiose, arbutin and salicin. The mutationally activated cel operon is induced in the presence of its substrates, and is repressed in their absence. A comparison of proteins encoded by the cel operon with functionally equivalent proteins of the bgl operon, another cryptic E. coli gene system responsible for the catabolism of beta-glucoside sugars, revealed no significant homology between these two systems despite common functional characteristics. The celD and celF encoded repressor and phospho-beta-glucosidase proteins are homologous to the melibiose regulatory protein and to the melA encoded alpha-galactosidase of E. coli, respectively. Furthermore, the celC encoded PEP-dependent phosphotransferase system enzyme IIIcel is strikingly homologous to an enzyme IIIlac of the Gram-positive organism Staphylococcus aureus. We conclude that the genes for these two enzyme IIIs diverged much more recently than did their hosts, indicating that E. coli and S. aureus have undergone relatively recent exchange of chromosomal genes.

Glucose metabolism by K+-limitedKlebsiella aerogenes: Evidence for the involvement of a quinoprotein glucose dehydrogenase

Like other members of the Enterobacteriaceae, Klebsiel la aerogenes transports glucose into the cell by means of a PEP-dependent phosphotransferase system (PTS; for review see [1]). This system has a high affinity for glucose and, not surprisingly, was found to be exceedingly active in cells of a slowly growing glucose-limited chemostat culture (apparent specific activity > 250 nmo l /min . (mg dry wt cells)-1 at D = 0 .1 /h [2]). Interestingly, the apparent activity of this system declined sharply as the growth rate was increased such that, at growth rates greater than 0.7/h, its activity was lower than that necessary to account for the actual rate of glucose uptake by the growing cells. More significantly, glucose-sufficient cultures (that were K +-, phosphateor ammonia-limited) consumed glucose at substantially higher rates than the corresponding glucose-limited culture, yet seemingly possessed uniformly low glucose-PTS activities. These discrepancies suggested that, at the higher growth rates a n d / o r with glucose-sufficient conditions, ancillary systems might contribute substantially to the overall rate of glucose flux, though such a supposition rested heavily on the assumption that the apparent glucose-PTS activity measured in vitro approximated closely to the actual activity of the undisturbed cells. However, the further observation that some glucose-sufficient cultures excreted gluconic and 2-ketoghiconic acid in substantial amounts [3] again pointed to the possibility of there being present in K. aerogenes processes of glucose catabolism that might not directly involve the glucose-PTS. Hence we undertook a search for this putative alternative glucosemetabolizing system which resulted in the finding of a quinoprotein glucose dehydrogenase (EC 1.1.99.17). To the best of our knowledge, this enzyme has not previously been reported to be present in K. aerogenes, or in related species.

Non-vectorial phosphorylation by the bacterial PEP-dependent phosphotransferase system is an artifact of spheroplast and membrane vesicle preparation procedures

These data demonstrate that the phenomenon of non-vectorial phosphorylation [Saier, M.H. jr and Schmidt, M.R. (1981) J. Bacteriol. 145, 391–397] is an experimental artifact which arises during the conversion of whole cells to spheroplasts or membrane vesicles. It can be explained by a certain population of particles which are not properly sealed. There is no need to envoke two orientations of enzyme II in the membrane, one of which would have no physiological significance.

Cloning and expression in Escherichia coli of the sucrase gene from Bacillus subtilis.

A recombinant cosmid carrying the sucrase gene (sacA) was obtained from a colony bank of E. coli harboring recombinant cosmids representative of the B. subtilis genome. It was shown that the sacA gene is located in a 2kb EcoRI fragment and that the cloned sequence is homologous to the corresponding chromosomal DNA fragment. A fragment of 2kb containing the gene was subcloned in both orientations in the bifunctional vector pHV33 and expression was further looked for in B. subtilis and E. coli. Complementation of a sacA mutation was observed in Rec+ and REc- strains of B. subtilis. Expression of sucrase was also demonstrated in E. coli, which is normally devoid of this activity, by SDS-polyacrylamide gel electrophoresis, specific immunoprecipitation and assay of the enzyme in crude extracts. The specific activity of the enzyme depended on the orientation of the inserted fragment. The saccharolytic activity was found to be cryptic in E. coli since the presence of the recombinant plasmids did not allow the transport of [U14C] sucrose and the growth of the cells. It was shown also that the recombinant cosmid contained part of the neighboring locus (sacP) which corresponds to a component of the PEP-dependent phosphotransferase system of sucrose transport of B. subtilis.

Escherichia coli phosphoenolpyruvate-dependent phosphotransferase system: mechanism of the phosphoryl-group transfer from phosphoenolpyruvate to HPr

The mechanism of phosphoryl-group transfer from phosphoenolpyruvate (PEP) to HPr, catalyzed by enzyme I of the Escherichia coli PEP-dependent phosphotransferase system, has been studied in vitro. Steady-state kinetics and isotope exchange measurements revealed that this reaction cannot be described by a classical ping-pong mechanism although phosphoenzyme I acts as an intermediate. The kinetic data indicate that HPr and PHPr occupy binding sites on enzyme I that do not overlap with the binding sites for PEP and pyruvate. As a result, binding interactions between HPr and enzyme I exist regardless of their phosphorylated state. A general mechanism is presented that describes the phosphorylation of HPr. The physiological implications of this mechanism are discussed.

The bacterial pep-dependent phosphotransferase system mechanism of gluconate phosphorylation in Streptococcus faecalis

The bacterial pep-dependent phosphotransferase system mechanism of gluconate phosphorylation in Streptococcus faecalis