Isolation, cloning, and expression of an acid phosphatase containing phosphotyrosyl phosphatase activity from Prevotella intermedia

Exploiting Acid Phosphatases in the Synthesis of Phosphorylated Monoalcohols and Diols

A set of phosphatases was evaluated for their potential to catalyze the regio‐ and stereoselective phosphorylation of alcohols using a high‐energy inorganic phosphate donor, such as di‐, tri‐ and polyphosphate. Parameters such as type and amount of phosphate donor and pH of the reaction were investigated in order to minimize the thermodynamically favored hydrolysis of the phosphate donor and the formed phosphate ester. Diols were monophosphorylated with high selectivities. This biocatalytic phosphorylation method provides selectively activated and/or protected synthetic intermediates for further chemical and/or enzymatic transformations and is applicable to a large scale (6.86 g) in a flow setup with immobilized phosphatase.

Identification and characterization of novel membrane-bound PRL protein tyrosine phosphatases from Setaria cervi, a bovine filarial parasite

A significant amount of protein tyrosine phosphatase (PTP) activity was detected in the detergent-soluble membrane-bound fraction of Setaria cervi, a bovine filarial parasite. The membrane-bound PTP activity was significantly inhibited when the adult parasites were exposed to compounds having antifilarial activity like aspirin and SK7 as well as phenylarsine oxide, a specific PTP inhibitor suggesting that this activity is stress regulated. Further, this enzyme was purified as a single protein of apparently 21 kDa using two different chromatographic techniques. The MALDI-MS/MS analysis of its peptides showed closest match with protein tyrosine phosphatase PRL (Aedes aegypti). This purified enzyme (named as PRL) showed maximum activity at pH 5.5/37 °C and hydrolysed para nitro phenyl phosphate (pNPP) at the highest rate followed by O-P-L-tyrosine and O-P-L-threonine. It showed significant inhibition by specific inhibitors of PTP such as sodium orthovanadate, phenylarsine oxide and ammonium molybdate and was activated by dithiothreitol (DTT). The active site modification studies suggested involvement of cysteine, arginine, histidine and aspartic acid in the catalytic activity of PRL. The activity of S. cervi PRL was also found to be resistant towards the external oxidative stress. Thus, S. cervi PRL could be taken as a potential target for the management of human lymphatic filariasis.

Identification of a novel stress regulated FERM domain containing cytosolic protein having PTP activity in Setaria cervi, a bovine filarial parasite

A 67 kDa cytosolic FERM domain containing protein having significant protein tyrosine phosphatases activity (PTPL) has been purified to homogeneity from Setaria cervi, a bovine filarial parasite. The MALDI-MS/MS analysis of the purified protein revealed 16 peptide peaks showing nearest match to Brugia malayi Moesin/ezrin/radixin homolog 1 protein and one peptide showing significant similarity with a region lying in the catalytic domain of human PTPD1. PTPL showed significant cross reactivity with the human PTP1B antibody and colocalize with actin in the coelomyrian cells of hypodermis in the parasite. PTPL was stress regulated as it showed marked decrease in the expression when exposed to Aspirin, an antifilarial drug and Phenylarsine Oxide, PTP inhibitor.

Polar localization of PhoN2, a periplasmic virulence-associated factor of Shigella flexneri, is required for proper IcsA exposition at the old bacterial pole

Proper protein localization is critical for bacterial virulence. PhoN2 is a virulence-associated ATP-diphosphohydrolase (apyrase) involved in IcsA-mediated actin-based motility of S. flexneri. Herein, by analyzing a ΔphoN2 mutant of the S. flexneri strain M90T and by generating phoN2::HA fusions, we show that PhoN2, is a periplasmic protein that strictly localizes at the bacterial poles, with a strong preference for the old pole, the pole where IcsA is exposed, and that it is required for proper IcsA exposition. PhoN2-HA was found to be polarly localized both when phoN2::HA was ectopically expressed in a Escherichia coli K-12 strain and in a S. flexneri virulence plasmid-cured mutant, indicating a conserved mechanism of PhoN2 polar delivery across species and that neither IcsA nor the expression of other virulence-plasmid encoded genes are involved in this process. To assess whether PhoN2 and IcsA may interact, two-hybrid and cross-linking experiments were performed. While no evidence was found of a PhoN2-IcsA interaction, unexpectedly the outer membrane protein A (OmpA) was shown to bind PhoN2-HA through its periplasmic-exposed C-terminal domain. Therefore, to identify PhoN2 domains involved in its periplasmic polar delivery as well as in the interaction with OmpA, a deletion and a set of specific amino acid substitutions were generated. Analysis of these mutants indicated that neither the (183)PAPAP(187) motif of OmpA, nor the N-terminal polyproline (43)PPPP(46) motif and the Y155 residue of PhoN2 are involved in this interaction while P45, P46 and Y155 residues were found to be critical for the correct folding and stability of the protein. The relative rapid degradation of these amino acid-substituted recombinant proteins was found to be due to unknown S. flexneri-specific protease(s). A model depicting how the PhoN2-OmpA interaction may contribute to proper polar IcsA exposition in S. flexneri is presented.

MALDI mass sequencing and biochemical characterization of Setaria cervi protein tyrosine phosphatase

A 30-kDa acid phosphatase with protein tyrosine phosphatase activity was identified in Setaria cervi (ScPTP). The enzyme was purified to homogeneity using three-step column chromatography. Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) analysis of purified ScPTP yielded a total of eight peptides matching most closely to phosphoprotein phosphatase of Ricinus communis (RcPP). A hydrophilicity plot of RcPP revealed the presence of these peptides in the hydrophilic region, suggesting their antigenic nature. The substrate specificity of ScPTP with ortho-phospho-L-tyrosine and inhibition with sodium orthovanadate and ammonium molybdate affirmed it as a protein tyrosine phosphatase. ScPTP was also found to be tartrate resistant. The Km and Vmax were 6.60 mM and 83.3 μM/ml/min, respectively, with pNPP and 8.0 mM and 111 μM/ml/min, respectively, with ortho-phospho-L-tyrosine as the substrate. The Ki value with sodium orthovanadate was calculated to be 16.10 mM. Active site modification with DEPC, EDAC and pHMB suggested the presence of histidine, cysteine and aspartate at its active site. Thus, on the basis of MALDI-TOF and biochemical studies, it was confirmed that purified acid phosphatase is a PTP.

Enzymatic production of 5'-inosinic acid by a newly synthesised acid phosphatase/phosphotransferase

5'-Nucleotides including 5'-inosinic acid have characteristic taste and important application in various foods as flavour potentiators. The selective nucleoside acid phosphatase/phosphotransferase (AP/PTase) can catalyse the synthesis of 5'-nucleotides by transfer of phosphate groups. In this study, a 747-bp gene encoding AP/PTase from Escherichia blattae was synthesised. After expression, the recombinant AP/PTase was purified using nickel-NTA. The optimal temperature and pH of this enzyme were 30°C and 5.0, respectively. The activity was partially inhibited by metal ions such as Hg(2+), Ag(+) and Cu(2+), but not by chelating reagents such as EDTA. The values of K(m) and V(max) for inosine were 40 mM and 3.5 U/mg, respectively. Using this purified enzyme, 16.83 mM of 5'-IMP was synthesised from 37 mM of inosine and the molar yield reached 45.5%. Homology modelling and docking simulation were discussed.

Setaria cervi dual specific phosphatase: characterization and its effect on eosinophil degranulation

Setaria cervi, a bovine filarial parasite contains significant acid phosphatase (AcP) activity in its various life stages. Two forms of AcP were separated from somatic extract of adult female parasite using cation exchange, gel filtration and concavalin affinity chromatography. One form having a molecular mass of 79 kDa was characterized as dual specific protein tyrosine phosphatase (ScDSP) based on substrate specificity and inhibition studies. With various substrates tested, it showed significant activity in the order of phospho-L-tyrosine>pNPP>ADP>phospho-L-serine. Inhibition by orthovanadate, fluoride, molybdate, and zinc ions further confirms protein tyrosine phosphatase nature of the enzyme. Km and Vmax determined with various substrates were found to be 16.66 mM, 25.0 microM/ml/min with pNPP; 20.0 mM, 40.0 microM/ml/min with phospho-L-tyrosine and 27.0 mM, 25.0 microM/ml/min with phospho-L-serine. KI with pNPP and sodium orthovanadate (IC50 33.0 microM) was calculated to be 50.0 mM. Inhibition with pHMB, silver nitrate, DEPC and EDAC suggested the presence of cysteine, histidine and carboxylate residues at its active site. Cross-reactivity with W. bancrofti-infected sera was demonstrated by Western blotting. ScDSP showed elevated levels of IgE in chronic filarial sera using ELISA. Under in vitro conditions, ScDSP resulted in increased effector function of human eosinophils when stimulated by IgG, which showed a further decrease with increasing enzyme concentration. Results presented here suggest that S. cervi DSP should be further studied to determine its role in pathogenesis and the persistence of filarial parasite.

Gene expression profile and pathogenicity of biofilm-forming Prevotella intermedia strain 17

BACKGROUND

Prevotella intermedia (P. intermedia), a gram-negative, black-pigmented anaerobic rod, has been implicated in the development of chronic oral infection. P. intermedia strain 17 was isolated from a chronic periodontitis lesion in our laboratory and described as a viscous material producing strain. The stock cultures of this strain still maintain the ability to produce large amounts of viscous materials in the spent culture media and form biofilm-like structures. Chemical analyses of this viscous material showed that they were mainly composed of neutral sugars with mannose constituting 83% of the polysaccharides. To examine the biological effect of the extracellular viscous materials, we identified and obtained a naturally-occurring variant strain that lacked the ability to produce viscous materials in vitro from our stock culture collections of strain 17, designated as 17-2. We compared these two strains (strains 17 versus 17-2) in terms of their capacities to form biofilms and to induce abscess formation in mice as an indication of their pathogenicity. Further, gene expression profiles between these two strains in planktonic condition and gene expression patterns of strain 17 in solid and liquid cultures were also compared using microarray assays.

RESULTS

Strain 17 induced greater abscess formation in mice as compared to that of the variant. Strain 17, but not 17-2 showed an ability to interfere with the phagocytic activity of human neutrophils. Expression of several genes which including those for heat shock proteins (DnaJ, DnaK, ClpB, GroEL and GroES) were up-regulated two to four-fold with statistical significance in biofilm-forming strain 17 as compared to the variant strain 17-2. Strain 17 in solid culture condition exhibited more than eight-fold up-regulated expression levels of several genes which including those for levanase, extracytoplasmic function-subfamily sigma factor (sigmaE; putative) and polysialic acid transport protein (KpsD), as compared to those of strain 17 in liquid culture media.

CONCLUSION

These results demonstrate that the capacity to form biofilm in P. intermedia contribute to their resistance against host innate defence responses.

Comparative analysis of putative periodontopathic bacteria by multiplex polymerase chain reaction

BACKGROUND AND OBJECTIVE

The polymerase chain reaction (PCR) has been applied for the rapid and specific detection of periodontopathic bacteria in subgingival plaque and is potentially of clinical benefit in the diagnosis and treatment of periodontitis subjects. However, several technical points need to be modified before the conventional PCR detection system can be used by clinicians.

MATERIAL AND METHODS

To develop a PCR-based technique more applicable for clinical use than conventional PCR, we established a multiplex PCR for five putative periodontopathic (Treponema denticola, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Prevotella intermedia and Tannerella forsythia) and two nonperiodontopathic (Streptococcus sanguinis and Streptococcus salivarius) species of bacteria using whole-plaque suspension as templates, and detected bacteria in subgingival plaque taken from 85 subjects at the supportive periodontal therapy stage after active periodontal treatments.

RESULTS

Among putative periodontopathic bacteria, the detection frequency of T. denticola and P. gingivalis was elevated in parallel with higher probing pocket depth and clinical attachment loss, and had 4.2-14.1 times increasing odds of the clinical parameters tested. Detection of any of the five species of putative periodontopathic bacteria markedly increased the odds ratio of a higher probing pocket depth, clinical attachment loss and bleeding on probing.

CONCLUSION

The multiplex PCR system developed in this study enabled the detection of all the bacteria under investigation in one reaction tube in a less time- and labor-intensive manner than conventional PCR. These results support the potential clinical use of multiplex PCR for detecting periodontopathic bacteria and for evaluating therapeutic strategies and predicting the prognosis for each subject.

Protein engineering of class-A non-specific acid phosphatase (PhoN) of Salmonella typhimurium: modulation of the pH-activity profile

Engineering of the PhoN enzyme of Salmonella typhimurium due to its superior characteristics for bioremediation of heavy metals has been advocated by Macaskie and colleagues [Basnakova, G., Stephens, E.R., Thaller, M.C., Rossolini, G.M., Macaskie, L.E., 1998. The use of Escherichia coli bearing a phoN gene for the removal of uranium and nickel from aqueous flows. Appl. Microbiol. Biotechnol. 50, 266-272]. The native enzyme hydrolyzes disparate organophosphates and exhibits optimal phosphatase activity at pH 5.5, for instance, with substrate p-nitrophenyl phosphate. Structurally guided Ile-78 was mutated using site-directed mutagenesis to Ala, Asp and His residues, with an aim to shift the optimum pH of the PhoN enzyme. Encouragingly, the I78A mutant displays significantly higher (as high as 160%) enzymatic efficiency over a broad pH range of 3.0-9.0, compared to the wild-type PhoN. The higher catalytic efficiency is due to the increase in k(cat), and can be mainly attributed to a deshielding of catalytic His-158 from the bulk-solvent. The I78D mutant possesses nearly twice the specific activity at the optimum pH of 7.0. The alkaline shift of the pH-activity profile agrees well with reasoning based on electrostatics. An increase in K(m), however, lowers the catalytic efficiency of the I78D mutant at the optimum pH. The I78H mutant, counter-intuitively, also exhibits an alkaline shift in the pH-optimum. Nonetheless, the active site scaffold in I78H mutant may not be disturbed, as similar steady-state kinetic parameters are observed for both I78H mutant and wild-type PhoN at their respective pH optima.

Acid phosphatase/phosphotransferases from enteric bacteria

We have investigated the enzymatic phosphorylation of nucleosides and found that Morganella morganii phoC acid phosphatase exhibits regioselective pyrophosphate (PP(i))-nucleoside phosphotransferase activity. In this study, we isolated genes encoding an acid phosphatase with regioselective phosphotransferase activity (AP/PTase) from Providencia stuartii, Enterobacter aerogenes, Escherichia blattae and Klebsiella planticola, and compared the primary structures and enzymatic characteristics of these enzymes with those of AP/PTase (PhoC acid phosphatase) from M. morganii. The enzymes were highly homologous in primary structure with M. morganii AP/PTase, and are classified as class A1 acid phosphatases. The synthesis of inosine-5'-monophosphate (5'-IMP) by E. coli overproducing each acid phosphatase was investigated. The P. stuartii enzyme, which is most closely related to the M. morganii enzyme, exhibited high 5'-IMP productivity, similar to the M. morganii enzyme. The 5'-IMP productivities of the E. aerogenes, E. blattae and K. planticola enzymes were inferior to those of the former two enzymes. This result underlines the importance of lower K(m) values for efficient nucleotide production. As these enzymes exhibited a very high degree of homology at the amino acid sequence level, it is likely that local sequence differences in the binding pocket are responsible for the differences in the nucleoside-PP(i) phosphotransferase reaction.

Use of the genomic subtractive hybridization technique to develop a real-time PCR assay for quantitative detection of Prevotella spp. in oral biofilm samples

Genomic subtractive hybridization was used to design Prevotella nigrescens-specific primers and TaqMan probes. Based on this technique, a TaqMan real-time PCR assay was developed for quantifying four oral black-pigmented Prevotella species. The combination of real-time PCR and genomic subtractive hybridization is useful for preparing species-specific primer-probe sets for closely related species.

BcrC from Bacillus subtilis Acts as an Undecaprenyl Pyrophosphate Phosphatase in Bacitracin Resistance

Overexpression of the BcrC(Bs) protein, formerly called YwoA, in Escherichia coli or in Bacillus subtilis allows these bacteria to stand higher concentrations of bacitracin. It was suggested that BcrC(Bs) was a membrane-spanning domain of an ATP binding cassette (ABC) transporter involved in bacitracin resistance. However, we hypothesized that this protein has an undecaprenyl pyrophosphate (UPP) phosphatase activity able to compete with bacitracin for UPP. We found that overexpression of a recombinant His6-BcrC(Bs) protein in E. coli (i) increased the resistance of the cells to bacitracin and (ii) increased UPP phosphatase activity in membrane preparations by 600-fold. We solubilized and prepared an electrophoretically pure protein exhibiting a strong UPP phosphatase activity. BcrC(Bs), which belongs to the type 2 phosphatidic acid phosphatase (PAP2) phosphatase superfamily (PF01569), differs totally from the already known BacA UPP phosphatase from E. coli, a member of the PF02673 family of the Protein family (Pfam) database. Thus, BcrC(Bs) and its orthologs form a new class of proteins within the PAP2 phosphatase superfamily, and likely all of them share a UPP phosphatase activity.

Multiplex polymerase chain reaction assay for simultaneous detection of black-pigmented Prevotella species in oral specimens

Prevotella species are a major component of the oral microflora and some have been implicated in various forms of periodontal disease. Despite the importance of understanding the prevalence of these organisms in the oral microflora, no rapid, simultaneous detection system for these species has been reported. This study developed a multiplex polymerase chain reaction assay for the simultaneous detection of four oral black-pigmented Prevotella species in various oral specimens. This assay will be useful for determining the prevalence of these organisms in the oral ecosystem. Furthermore, this assay system should prove a useful tool for analyzing the role of black-pigmented Prevotella species in the mouth.

A novel exopolysaccharide from a clinical isolate of Prevotella nigrescens: purification, chemical characterization and possible role in modifying human leukocyte phagocytosis

Prevotella nigrescens, a gram-negative black-pigmented anaerobic rod, has frequently been isolated from periodontitis and periapical periodontitis lesions. We have isolated an exopolysaccharide-producing P. nigrescens, strain 22, from a chronic periodontitis lesion. The purpose of this study was to determine the chemical composition and function of the exopolysaccharide associated with this clinical isolate. The chemical composition and structure of the purified exopolysaccharide from strain 22 were determined by high performance liquid chromatography and methylation analysis. To define the biological function of this exopolysaccharide, a chemically induced exopolysaccharide nonproducing mutant, strain 328, which was derived from strain 22, was established. The biological effects of exopolysaccharide were determined by comparing the ability of strain 22, strain 328 or heat-killed strain 22 to form abscesses in mice and to interfere with the phagocytic activity of peripheral blood polymorphonuclear leukocytes. Chemical analysis showed that isolated exopolysaccharide consisted of mannose (521.6 microg/mg), glucose (25.6 microg/mg), fructose (65.8 microg/mg), galactose (12.5 microg/mg), arabinose (6.2 microg/mg), xylose (3.2 microg/mg), rhamnose (6.1 microg/mg), and ribose (0.6 microg/mg). Methylation analysis of exopolysaccharide indicated that the linkages of mannose were primarily (1-->2, 1-->6) (1-->2) (1-->6), and (1-->3). Strain 22 and, to a lesser extent, its heat-killed counterpart induced greater abscess formation in mice than strain 328, even though the enzymatic profile of strain 22 was similar to that of strain 328. The ability of strain 328 to induce abscess formation was restored by adding the purified exopolysaccharide isolated from strain 22 to the cell suspension of strain 328. Exopolysaccharide alone failed to induce abscess formation in mice. Further, strain 328 but not the untreated or heat-killed strain 22, was phagocytosed by polymorphonuclear leukocytes both in the presence and in the absence of opsonic factors. The results suggest that these polysaccharides isolated from strain 22, which primarily consisted of mannose, may play a key role in the development of the chronic inflammatory lesion from which this strain was isolated.

Inhibitory effects of green tea catechins on protein tyrosine phosphatase in Prevotella intermedia

Members of the Prevotella intermedia group possess protein tyrosine phosphatase (PTPase). The purpose of this study was to investigate the effects of catechin derivatives from Japanese green tea on the activity of PTPase in P. intermedia and related organisms. Multilocus enzyme electrophoresis of alkaline phosphatase derived from P. intermedia, Prevotella nigrescens, Prevotella pallens and Porphyromonas gingivalis revealed a species-specific migration pattern. Among the tea catechin derivatives tested, (-)-epigallocatechin gallate (EGCg), similar to orthovanadate, a specific inhibitor for PTPase, was effective in inhibiting the PTPase activity in P. intermedia at 0.5 microm, and related species at 5 microm. The results suggested that the inhibitory effect observed is due to the presence of galloyl moiety in the structure. In contrast, neither the green tea catechins nor orthovanadate inhibited the phosphatase activity in P. gingivalis, suggesting that this organism possessed a different family of alkaline phosphatase.

Shigella apyrase--a novel variant of bacterial acid phosphatases?

A virulence-associated ATP diphosphohydrolase activity in the periplasm of Shigella, identified as apyrase, was found to be markedly similar to bacterial non-specific acid phosphatases in primary structure. When the Shigella apyrase sequence was threaded in to the recently published 3D structure of the highly similar (73%) Escherichia blattae acid phosphatase it was found to have a highly overlapping 3D structure. Our analysis, which included assays for phosphatase, haloperoxidase and catalase activities, led us to hypothesize that Shigella apyrase might belong to a new class of pyrophosphatase originating as one more variant in the family of bacterial non-specific acid phosphatases. It revealed interesting structure-function relationships and probable roles relevant to pathogenesis.

Kinetic analysis of PPi-dependent phosphofructokinase from Porphyromonas gingivalis

We have previously cloned the gene encoding a pyrophosphate-dependent phosphofructokinase (PFK), designated PgPFK, from Porphyromonas gingivalis, an oral anaerobic bacterium implicated in advanced periodontal disease. In this study, recombinant PgPFK was purified to homogeneity, and biochemically characterized. The apparent K(m) value for fructose 6-phosphate was 2.2 mM, which was approximately 20 times higher than that for fructose 1,6-bisphosphate. The value was significantly greater than any other described PFKs, except for Amycolatopsis methanolica PFK which is proposed to function as a fructose 1,6 bisphosphatase (FBPase). The PgPFK appears to serves as FBPase in this organism. We postulate that this may lead to the gluconeogenic pathways to synthesize the lipopolysaccharides and/or glycoconjugates essential for cell viability.