Helicobacter pylori enzymes

A remarkable peroxidase-like behavior of the catalase KatA from the pathogenic bacteria Helicobacter pylori: The oxidation reaction with formate as substrate and the stabilization of an [Fe(IV) = O Trp•] intermediate assessed by multifrequency EPR spectroscopy

We have characterized the catalytic cycle of the Helicobacter pylori KatA catalase (HPC). H. pylori is a human and animal pathogen responsible for gastrointestinal infections. Multifrequency (9-285 GHz) EPR spectroscopy was applied to identify the high-valent intermediates (5 ≤ pH ≤ 8.5). The broad (2000 G) 9-GHz EPR spectrum consistent with the [Fe(IV) = O Por•+] intermediate was detected, and showed a clear pH dependence on the exchange-coupling of the radical (delocalized over the porphyrin moiety) due to the magnetic interaction with the ferryl iron. In addition, Trp• (for pH ≤ 6) and Tyr• (for 5 ≤ pH ≤ 8.5) species were distinguished by the advantageous resolution of their g-values in the 285-GHz EPR spectrum. The unequivocal identification of the high-valent intermediates in HPC by their distinct EPR spectra allowed us to address their reactivity towards substrates. The stabilization of an [Fe(IV) = O Trp•] species in HPC, unprecedented in monofunctional catalases and possibly involved in the oxidation of formate to the formyloxyl radical at pH ≤ 6, is reminiscent of intermediates previously identified in the catalytic cycle of bifunctional catalase-peroxidases. The 2e- oxidation of formate by the [Fe(IV) = O Por•+] species, both at basic and acidic pH conditions, involving a 1H+/2e- oxidation in a cytochrome P450 peroxygenase-like reaction is proposed. Our findings demonstrate that moonlighting by the H. pylori catalase includes formate oxidation, an enzymatic reaction possibly related to the unique strategy of the neutrophile bacterium for gastric colonization, that is the release of CO2 to regulate the pH in the acidic environment.

Global Trend on Machine Learning in Helicobacter within One Decade: A Scientometric Study

Purpose

This study aims to create a science map, provide structural analysis, investigate evolution, and identify new trends in Helicobacter pylori (H. pylori) research articles.

Methods

All Helicobacter publications were gathered from the Web of Science (WoS) database from August 2010 to 2021. The data were required for bibliometric analysis. The bibliometric analysis was performed with Bibliometrix R Tool. Bibliometric data were analyzed using the Bibliometrix Biblioshiny R-package software.

Results

A total of 17,413 articles were reviewed and analyzed, with descriptive characteristics of the H. pylori literature included. In journals, 21,102 keywords plus and 20,490 author keywords were reported. These articles were also written by 56,106 different authors, with 262 being single-author articles. Most authors' abstracts, titles, and keywords included "Helicobacter-pylori." Since 2010, the total number of H. pylori-related publications has been decreasing. Gut, PLOS ONE, and Gastroenterology are the most influential H. pylori journals, according to source impact. China, the United States, and Japan are the countries with most affiliations and subjects. In addition, Seoul National University has published the most articles about H. pylori. According to the cloud word plot, the authors' most frequently used keywords are gastric cancer (GC), H. pylori, gastritis, eradication, and inflammation. "Helicobacter pylori" and "infection" have the steepest slopes in terms of the upward trend of words used in articles from 2010 to 2021. Subjects such as GC, intestinal metaplasia, epidemiology, peptic ulcer, eradication, and clarithromycin are included in the diagram's motor theme section, according to strategic diagrams. According to the thematic evolution map, topics such as Helicobacter pylori infection, B-cell lymphoma, CagA, Helicobacter pylori, and infection were largely discussed between 2010 and 2015. From 2016 to 2021, the top topics covered included Helicobacter pylori, H. pylori infection, and infection.

Acute Bowel Computed Tomography

Acute abdominal pain is a common presenting complaint in the emergency department. Increasingly, computed tomography is utilized for evaluating these patients. Radiologists are therefore expected to be familiar with the pertinent clinical and radiologic information related to acute bowel pathology. This primer will review the need-to-know and latest updates related to computed tomography evaluation of acute bowel pathology.

The Forgotten Virulence Factor: The 'non-conventional' Hemolysin TlyA And Its Role in Helicobacter pylori Infection

Helicobacter pylori is a human-specific Gram-negative pathogenic bacterium which colonizes the gastric mucosal layer in the stomach causing diseases such as peptic ulcer, adenocarcinoma, and gastric lymphoma. It is estimated that approximately half of the world's population is infected with H. pylori making it the most intensively characterized microbial pathogen up to now. Hemolysis has been suggested to significantly contribute to colonization of the stomach and disease progression by H. pylori. In a number of earlier studies, TlyA was characterized as a putative pore-forming cytolysin. Although a few observations in the literature suggest a role for TlyA as significant virulence factor of H. pylori, the molecular and structural characterization of this protein is much curtailed at present. Given the intensive characterization of numerous H. pylori virulence factors over the past decade, surprisingly little information exists for the TlyA toxin and its significance for pathogenesis. This review provides a brief overview on microbial hemolysis and its role for pathogenesis and discusses recent research efforts aimed at an improved understanding of the role of the 'non-conventional' hemolysin and its associated RNA methyltransferase TlyA from H. pylori.

Recent progress on phospholipases: different sources, assay methods, industrial potential and pathogenicity

Significant studies on phospholipases optimization, characterization, physiological role and industrial potential have been conducted worldwide. Some of them have been directed for biotechnological advances such as gene discovery and functional enhancement by protein engineering. Others reported phospholipases as virulence factor and major cause of pathophysiological effects. A general overview on phospholipase is needed for the identification of new reliable and efficient phospholipase, which would be potentially used in number of industrial and medical applications. Phospholipases catalyse the hydrolysis of one or more ester and phosphodiester bonds of glycerophospholipids. They vary in site of action on phospholipid which can be used industrially for modification/production of new phospholipids. Catalytically active phospholipase mainly use phosphatidylcholine as major substrate, but they can also show specificity with other phospholipids. Several accurate phospholipase assay methods are known, but a rapid and reliable method for high-throughput screening is still a challenge for efficient supply of superior phospholipases and their practical applications. Major application of phospholipase is in industries like oil refinery, health food manufacturing, dairy, cosmetics etc. All types of phospholipases can be involved as virulence factor. They can also be used as diagnostic markers for microbial infection. The importance of phospholipase in virulence is proven and inhibitors of the enzyme can be used as candidate for preventing the associated disease.

Phospholipase A in Gram-negative bacteria and its role in pathogenesis

Phospholipase A (PLA) is one of the few enzymes present in the outer membrane of Gram-negative bacteria, and is likely to be involved in the membrane disruption processes that occur during host cell invasion. Both secreted and membrane-bound phospholipase A(2) activities have been described in bacteria, fungi and protozoa. Recently there have been increasing reports on the involvement of PLA in bacterial invasion and pathogenesis. This review highlights the latest findings on PLA as a virulence factor in Gram-negative bacteria.

The class C acid phosphatase of Helicobacter pylori is a 5' nucleotidase

The results from purification and characterization studies of the hppA gene product of Helicobacter pylori confirm its identification as a class C acid phosphatase. The hppA gene of H. pylori ATCC strain 49503 was amplified and modified by PCR, cloned into pET21b, and overexpressed in Escherichia coli. The recombinant protein was liberated from membranes and purified (16x) to apparent homogeneity with cation exchange and Ni-chelate chromatography resulting in a recovery of 39% of total starting activity. The recombinant acid phosphatase exhibited a denatured molecular mass of 24 kDa by SDS-PAGE. Phosphatase activity in both crude and purified samples could be renatured and detected after SDS-PAGE. The native molecular mass of recombinant enzyme was approximately 72 kDa by gel filtration chromatography on Superdex 75. While phosphate and tartrate had little effect on phosphatase activity, molybdate, vanadate, and EDTA had significant inhibitory effects on enzymatic activity. Phosphomonoesterase activity for hydrolysis of p-nitrophenylphosphate (pNPP) as well as other substrates was enhanced in the presence of divalent cations including Cu(2+), Ni(2+), Co(2+), and Mg(2+). Recombinant HppA had narrow substrate specificity with highest activity for arylphosphates and significant activity for 5' nucleoside monophosphates. The pH optimum for enzyme activity was 4.6 and 5.2 for purine and pyrimidine 5' monophosphates, respectively. The affinity constants for the 5' nucleoside monophosphates were found to be 0.5-1 mM. Results from this study confirm HppA inclusion in the class C acid phosphatases and led to its identification as a 5' nucleotidase.

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Recombinant Helicobacter pylori catalase

AIM: To construct a recombinant strain which highly expresses catalase of Helicobacter pylori (H. pylori) and assay the activity of H. pylori catalase.

METHODS: The catalase DNA was amplified from H. pylori chromosomal DNA with PCR techniques and inserted into the prokaryotie expression vector pET-22b (+), and then was transformed into the BL21 (DE3) E. coli strain which expressed catalase recombinant protein. The activity of H. pylori catalase was assayed by the Beers&Sizers.

RESULTS: DNA sequence analysis showed that the sequence of catalase DNA was the same as GenBank’s research. The catalase recombinant protein amounted to 24.4% of the total bacterial protein after induced with IPTG for 3 hours at 37 °C and the activity of H. pylori catalase was high in the BL21 (DE3) E. coli strain.

CONCLUSION: A clone expressing high activity H. pylori catalase is obtained, laying a good foundation for further studies.

Normalization of phospholipids concentration of the gastric mucosa was observed in patients with peptic ulcer after eradication of Helicobacter pylori

BACKGROUND

Phospholipids concentration in the gastric mucosa decreased in patients with Helicobacter pylori infection. The aim of this study is to examine the effects of eradication of H. pylori on decreasing the phospholipids concentration in the gastric mucosa in patients with gastric or duodenal ulcer.

MATERIALS AND METHODS

Phospholipids (phosphatidylcholine, phosphatidylethanolamine, and sphingonomyeline) were measured in biopsy specimens from the antrum and corpus using thin-layer chromatography. In H. pylori positive patients with gastric ulcer (n = 26) and duodenal ulcer (n = 13), and H. pylori negative controls (n = 20), the biopsy specimens were obtained before and 3 months after eradication. Eradication was performed using lansoprazole, amoxycillin, and clarithromycin.

RESULTS

Compared with the H. pylori negative control group, the concentrations of phosphatidylcholine and phosphatidylethanolamine decreased significantly in the gastric ulcer group in both antrum and corpus mucosa, and in the duodenal ulcer group in antrum mucosa. This decrease returned to the control level after eradication.

CONCLUSIONS

This study demonstrates that the eradication of H. pylori in patients with peptic ulcer normalized the decrease of phosphatidylcholine and phosphatidylethanolamine in the gastric mucosa.

Helicobacter pylori infection and migraine

The study is aimed to ascertain whether the Helicobacter pylori (Hp) infection is responsible for the vulnerability to oxidative stress observed in migraineurs. Hp serological positivity was assessed by ELISA evaluation of specific IgA and IgG antibodies in 30 subjects (11 males and 19 females) suffering from migraine without aura during the headache-free period. The Hp infection was detected in 16.7% of migraineurs. Plasma accumulation of peroxidative substances (TBA-RS), an index of systemic oxidative status, was increased in migraineurs without Hp infection with respect to controls (P< 0.001), while no significant differences of TBA-RS were found in migraineurs with or without Hp infection. Unmodified values of plasma nitrite/nitrate concentrations, expression of systemic nitric oxide (NO), were obtained in migraineurs in comparison to controls indicating that Hp infection does not modify the plasma oxidative status and the systemic NO bioavailability of migraineurs. In conclusion, our results do not support any specific correlation between Hp infection and migraine.

Helicobacter pylori infection and the use of NSAIDs

Helicobacter pylori infection and the use of non-steroidal anti-inflammatory drugs (NSAIDs) can each result in gastroduodenal ulcers and ulcer complications. Recent studies have suggested that there is an interaction between the two causes such that elimination of H. pylori before NSAID treatment decreases the occurrence of ulcers. This led to the conclusion of the Maastricht 2000 meeting that H. pylori eradication should be considered before embarking on long-term NSAID therapy. One of the main sources of confusion is related to the fact that prospective endoscopic studies testing various drugs for prevention of NSAID ulcers among chronic NSAID users are probably not directly applicable to problems of clinical ulcers and of ulcer complications. It has become clear that, to be interpretable clinically, such studies must provide separate analyses based on H. pylori status, history of ulcer, or an ulcer complication. Overall, the data strongly support the notion that eradication therapy is beneficial for primary prophylaxis. In contrast, one would expect little benefit when NSAIDs caused the clinical ulcer (secondary prevention) and, at best, H. pylori eradication has a modest effect on the prevention of recurrent ulcer bleeding in NSAID users who have suffered ulcer complications. The data support the notion that H. pylori eradication therapy should be given to all H. pylori -infected patients with peptic ulcers irrespective of whether or not they have used NSAIDs. Proton pump inhibitors are superior to placebo for the prevention of ulcer recurrence but are inferior to full-dose misoprostol for the prevention of ulcers among those with NSAID ulcers and no H. pylori infection. Selective COX-2 inhibitors appear to reduce markedly, but not eliminate, ulcer complications among chronic NSAID users.

Helicobacter pylori pore-forming cytolysin orthologue TlyA possesses in vitro hemolytic activity and has a role in colonization of the gastric mucosa

Hemolysins have been found to possess a variety of functions in bacteria, including a role in virulence. Helicobacter pylori demonstrates hemolytic activity when cultured on unlysed blood agar plates which is increased under iron-limiting conditions. However, the role of an H. pylori hemolysin in virulence is unclear. Scrutiny of the H. pylori 26695 genome sequence suggests the presence of at least two distinct hemolysins, HP1086 and HP1490, in this strain. Previous studies have shown that the in vitro hemolytic activity of H. pylori is reduced when it is coincubated with dextran 5000, suggesting the presence of a pore-forming cytolysin. HP1086 has homology to pore-forming cytolysins (TlyA) from other bacterial species, and the introduction of the cloned H. pylori tlyA gene into a nonhemolytic Escherichia coli strain conferred hemolytic activity. An H. pylori tlyA defined mutant showed reduced in vitro hemolytic activity, which appears to be due to pore formation, as the hemolytic activity of the wild-type strain is reduced to the same level as the tlyA mutant by the addition of dextran 5000. The mutant also showed reduced adhesion to human gastric adenocarcinoma cells and failed to colonize the gastric mucosa of mice. These data clearly suggest a role in virulence for H. pylori TlyA, contrary to the suggestion that hemolytic activity is an in vitro phenomenon for this pathogen.

Characterization of Helicobacter pylori PldA, a phospholipase with a role in colonization of the gastric mucosa

BACKGROUND & AIMS

Phospholipase activity may play a role in the pathogenicity of Helicobacter pylori. Furthermore, some drugs that are effective against H. pylori infection are phospholipase inhibitors. Scrutiny of the H. pylori 26695 genome sequence revealed the presence of a putative protein with homology to Esherichia coli outer membrane phospholipase A (PldA). The aim of this study was to investigate the role of this putative PldA in the pathogenicity of H. pylori.

METHODS

An isogenic pldA mutant was constructed and analyzed for in vitro phospholipase A(2) and hemolytic activity. Adherence of the mutant to human gastric adenocarcinoma cells and the ability to colonize mice were also investigated.

RESULTS

The pldA mutant showed a marked reduction in phospholipase A(2) and hemolytic activity compared with the wild-type strain. The mutant was unable to colonize mice at 2 and 8 weeks, but it did induce a significant immune response. In contrast, the ability of the mutant to adhere to human gastric adenocarcinoma cells was unaffected.

CONCLUSIONS

The results suggest a role for PldA in colonization of the gastric mucosa and possibly tissue damage after colonization.

Phospholipases A2 in gastric juice of Helicobacter pylori--positive and negative individuals

Gastric juice is known to have phospholipase A2 catalytic activity. Helicobacter pylori (H. pylori) has been reported to produce phospholipase A2, which is believed to hydrolyse the protective layer of gastric mucosal phospholipids and to promote mucosal damage. The current study aimed at identifying secretory phospholipase A2 subtypes (pancreatic group I phospholipase A2 and synovial-type group II phospholipase A2) in gastric juice and their relation to the presence of H. pylori in gastric mucosal biopsies in the same individuals. Gastric juice was collected from 29 individuals during gastroscopy. Biopsies were taken from the antrum and body of the stomach to determine the H. pylori status. We found catalytically active phospholipase A2 and both group I and group II phospholipases A2 in the gastric juice samples. The catalytic activity and the mass concentrations of group I and group II phospholipases A2 correlated significantly with the pH value in gastric juice. The gastric juice of H. pylori positive individuals did not contain higher amounts of phospholipases A2 than the juice of H. pylori negative individuals. Rather, the mass concentration of group II phospholipase A2 in gastric juice seemed to be somewhat lower in individuals with H. pylori infection than in uninfected individuals. The results of the current study show that both group I and group II phospholipases A2 are present in gastric juice. The main sources of phospholipases A2 in gastric juice are probably other than H. pylori.

Novel therapies for Helicobacter pylori infection

BACKGROUND

Increasing antibiotic resistance has begun to impair our ability to cure Helicobacter pylori infection.

AIM

To evaluate orally administered novel therapies for the treatment of H. pylori infection.

METHODS

Healthy H. pylori infected volunteers received: (a) hyperimmune bovine colostral immune globulins, (b) an oligosaccharide containing an H. pylori adhesion target, Neu5Aca2-3Galb1-4Glc-(3'-sialyllactose), or (c) recombinant human lactoferrin. Outcome was assessed by urea breath test or histological assessment of the number of H. pylori present.

RESULTS

None of the novel therapies appeared effective and no adverse events occurred.

CONCLUSION

Although in vitro data appeared promising, in vivo results were disappointing. Higher doses, longer duration of therapy, adjunctive acid suppression, or a combination could possibly yield better results.

A review of the possible bacterial determinants of clinical outcome inHelicobacter pyloriinfection

Helicobacter pylori is present in 40-60% of the population and approximately 10-20% of these infected individuals suffer from a H. pylori associated disease such as peptic ulcer disease or gastric cancer. This article reviews the potential bacterial determinants responsible for and markers predictive of both the acquisition of H. pylori infection and subsequent clinical outcome; i.e., asymptomatic infection or disease. The acquisition of H. pylori infection depends on exposure (hence the increased risk in lower socioeconomic groups and developing nations) to viable bacteria with at least a functional urease gene in a susceptible host. Once infection occurs, bacterial virulence factors, including the vacuolating cytotoxin, and genes of the cag pathogenicity island, as well as nonbacterial factors may determine disease outcome. Future research is being directed at discovering other bacterial virulence factors responsible for the different clinical outcomes of H. pylori infection. This will be greatly enhanced by the recent release of the complete genome sequence of H. pylori. The determination of the relative importance of each of these recognized and other as yet unrecognized factors responsible for disease outcome will assist in the appropriate targeting of patients in the treatment of H. pylori infection.Key words: Helicobacter pylori, genetics, virulence, bacterial.

Helicobacter pylori factors involved in the development of gastroduodenal mucosal damage and ulceration

Many putative virulence determinants of Helicobacter pylori are believed to trigger and worsen the gastroduodenal mucosa damage observed in infected patients. H. pylori urease reacts with the gastric urea and generates ammonia; ammonia combines with water and yields ammonium hydroxide, which is cytotoxic. Ammonia may also inhibit cell proliferation and cause indirect mucosal injury by stimulating neutrophils. Phospholipases may damage the gastric mucosa by degrading phospholipids and generating precursors of ulcerogenic components. Other enzymes, such as protease, neuraminidase, fucosidase, and alcohol dehydrogenase, can contribute to damage of the gastric epithelium by destroying the integrity of mucus or by inducing lipid peroxidation. Infection by vacuolating cytotoxic (VacA+) H. pylori strains is considered to constitute increased risk for development of peptic ulcer and gastric cancer. Exploration of the vacA gene structure has shown the existence of strongly toxigenic strains, and has confirmed at the molecular level the increased ulcerogenic potential of VacA+ H. pylori strains. A pathogenicity island called cag has been recently described in Type 1 H. pylori strains (VacA+/CagA+).cag contains the cagA gene (whose expression is associated with toxigenicity) and many genes, some of which are highly homologous to virulence genes of other virulent bacteria, that account for the enhanced pathogenic potential of CagA+ organisms.

Identifiable Helicobacter pylori strains or factors important in the development of duodenal ulcer disease

BACKGROUND

Helicobacter pylori is a primary pathogen as its presence in the stomach almost always is associated with a strong mucosal and systemic immune response. Putative virulence factors of H. pylori are numerous. In this article, we evaluate whether currently available evidence supports the existence of factors important in the development of duodenal ulcer disease.

METHODS

The evaluation is conducted by a review of the literature on H. pylori toxins and virulence factors.

RESULTS

Most putative H. pylori virulence factors are present in all isolates examined, though some are present only in, or are expressed more intensively by, determined strains. Urease is the main virulence determinant of H. pylori. It generates ammonia from the gastric urea, which in turn injures the gastric mucosa either directly by forming ammonium hydroxide or indirectly by stimulating polymorphonuclear leukocytes and inhibiting cell proliferation. Other enzymes (e.g., mucinase, phospholipases, alcohol dehydrogenase, neuraminidase) could promote tissue erosion and ulceration by destroying the integrity of mucus, by inducing lipid peroxidation, and the like. H. pylori strains that express the vacuolating toxin vacA and the associated protein cagA are called type I and are considered to be endowed with increased ulcerogenic and inflammatory potential. Exploration of the structure of the vacA gene has shown that the degree of toxicity is regulated at the molecular level. Type I H. pylori strains carry a 40-kb genomic fragment called cag that is absent from type II strains (vacA- and cagA-negative). cag is considered a pathogenicity island because it contains numerous genes that are highly homologous to virulence genes of classic bacterial pathogens and because it has been suggested that it is acquired through recombination events. CagA is part of the pathogenicity island. CagA-positive strains are more likely to be isolated from patients with duodenal ulcer and other severe digestive pathological processes.

CONCLUSIONS

The use of simple serological tests to identify patients infected with type I H. pylori strains could help to calculate the risk of development of severe gastroduodenal diseases and, possibly, to prevent such severe diseases.