Production of 4-hydroxybutyrate from succinate semialdehyde in butyrate biosynthesis in Porphyromonas gingivalis

Porphyromonas gingivalis in oral squamous cell carcinoma: A review

Oral cancer contributes significantly to the global cancer burden. Oral bacteria play an important role in the spread of oral cancer, according to mounting evidence. The most proven instance is the carcinogenic implications of Porphyromonas gingivalis, a key pathogen in chronic periodontitis. It is imperative to understand the pathogenesis of P. gingivalis in OSCC. This review aims to gather and assess scientific shreds of evidence on the involvement of Porphyromonas gingivalis in the molecular mechanism of oral squamous cell carcinoma.

Butyryl/Caproyl-CoA:Acetate CoA-transferase: cloning, expression and characterization of the key enzyme involved in medium-chain fatty acid biosynthesis

Coenzyme A transferases (CoATs) are important enzymes involved in carbon chain elongation, contributing to medium-chain fatty acid (MCFA) biosynthesis. For example, butyryl-CoA:acetate CoA transferase (BCoAT) is responsible for the final step of butyrate synthesis from butyryl-CoA. However, little is known about caproyl-CoA:acetate CoA-transferase (CCoAT), which is responsible for the final step of caproate synthesis from caproyl-CoA. In the present study, two CoAT genes from Ruminococcaceae bacterium CPB6 and Clostridium tyrobutyricum BEY8 were identified by gene cloning and expression analysis. Enzyme assays and kinetic studies were carried out using butyryl-CoA or caproyl-CoA as the substrate. CPB6-CoAT can catalyze the conversion of both butyryl-CoA into butyrate and caproyl-CoA into caproate, but its catalytic efficiency with caproyl-CoA as the substrate was 3.8-times higher than that with butyryl-CoA. In contrast, BEY8-CoAT had only BCoAT activity, not CCoAT activity. This demonstrated the existence of a specific CCoAT involved in chain elongation via the reverse β-oxidation pathway. Comparative bioinformatics analysis showed the presence of a highly conserved motif (GGQXDFXXGAXX) in CoATs, which is predicted to be the active center. Single point mutations in the conserved motif of CPB6-CoAT (Asp³⁴⁶ and Ala³⁵¹) led to marked decreases in the activity for butyryl-CoA and caproyl-CoA, indicating that the conserved motif is the active center of CPB6-CoAT and that Asp³⁴⁶ and Ala³⁵¹ have a significant impact on the enzymatic activity. This work provides insight into the function of CCoAT in caproic acid biosynthesis and improves understanding of the chain elongation pathway for MCFA production.

Analysis of the Butyrate-Producing Pathway in Porphyromonas gingivalis

Butyrate is one of the most harmful metabolic end products found in the oral cavity. Thus, it would be important to characterize the enzymes responsible for production of this metabolite to elucidate the pathogenicity of periodontogenic bacteria. Here, a spectrophotometric assay for butyryl-CoA:acetate CoA transferase activity and gas chromatography-mass spectrometry measurement of butyrate and other short chain fatty acids such as acetate, propionate, isobutyrate, and isovalerate are described.

Metabolic cooperativity between Porphyromonas gingivalis and Treponema denticola

Background

 Porphyromonas gingivalis and Treponema denticola are proteolytic periodontopathogens that co-localize in polymicrobial subgingival plaque biofilms, display in vitro growth symbiosis and synergistic virulence in animal models of disease. These symbioses are underpinned by a range of metabolic interactions including cooperative hydrolysis of glycine-containing peptides to produce free glycine, which T. denticola uses as a major energy and carbon source.

Objective

 To characterize the P. gingivalis gene products essential for these interactions. Methods: The P. gingivalis transcriptome exposed to cell-free T. denticola conditioned medium was determined using RNA-seq. P. gingivalis proteases potentially involved in hydrolysis of glycine-containing peptides were identified using a bioinformatics approach.

Results

 One hundred and thirty-twogenes displayed differential expression, with the pattern of gene expression consistent with succinate cross-feeding from T. denticola to P. gingivalis and metabolic shifts in the P. gingivalis folate-mediated one carbon superpathway. Interestingly, no P. gingivalis proteases were significantly up-regulated. Three P. gingivalis proteases were identified as candidates and inactivated to determine their role in the release of free glycine. P. gingivalis PG0753 and PG1788 but not PG1605 are involved in the hydrolysis of glycine-containing peptides, making free glycine available for T. denticola utilization.

Conclusion

 Collectively these metabolic interactions help to partition resources and engage synergistic interactions between these two species.

Amino acids as wetting agents: surface translocation by Porphyromonas gingivalis

Our understanding of how oral microbiota adapt in response to changes in their surroundings remains limited. This is particularly true of the slow-growing anaerobes that persist below the gum line. Here, we report that the oral anaerobe Porphyromonas gingivalis strain 381 can surface translocate when sandwiched between two surfaces. We show that during movement, this bacterium alters its metabolism, specifically side products of arginine utilization including citrulline and ornithine accumulated in the translocating cells; while arginine, N-acetyl-arginine, and the polyamine putrescine, which is produced from arginine were consumed. In addition, our results indicate that movement requires modification of the surrounding environment via proteolysis, cell dispersion, cell-on-cell rolling, and sub-diffusive cell-driven motility. We also show that production of fimbriae and fimbriae-associated proteins; as well as the regulation of contact-dependent growth inhibition genes, which are known to be involved in self-nonself discrimination, and the type IX secretion system are central to surface translocation. These studies provide a first glimpse into P. gingivalis motility and its relationship to ecological variables.

Separation of novel phosphoproteins of Porphyromonas gingivalis using phosphate-affinity chromatography

Phosphorylation of serine, threonine and tyrosine is a central mechanism for regulating the structure and function of proteins in both eukaryotes and prokaryotes. However, the action of phosphorylated proteins present in Porphyromonas gingivalis, a major periodontopathogen, is not fully understood. Here, six novel phosphoproteins that possess metabolic activities were identified, namely PGN_0004, PGN_0375, PGN_0500, PGN_0724, PGN_0733 and PGN_0880, having been separated by phosphate-affinity chromatography. The identified proteins were detectable by immunoblotting specific to phosphorylated Ser (P-Ser), P-Thr, and/or P-Tyr. These results imply that novel phosphorylated proteins might play an important role for regulation of metabolism in P. gingivalis.

Impact of micro-environmental changes on respiratory tract infections with intracellular bacteria

Community-acquired pneumonia is caused by intra- and extracellular bacteria, with some of these bacteria also being linked to the pathogenesis of chronic lung diseases, including asthma and chronic obstructive pulmonary disease. Chlamydia pneumoniae is an obligate intracellular pathogen that is highly sensitive to micro-environmental conditions controlling both pathogen growth and host immune responses. The availability of nutrients, as well as changes in oxygen, pH and interferon-γ levels, have been shown to directly influence the chlamydial life cycle and clearance. Although the lung has been traditionally regarded as a sterile environment, sequencing approaches have enabled the identification of a large number of bacteria in healthy and diseased lungs. The influence of the lung microbiota on respiratory infections has not been extensively studied so far and data on chlamydial infections are currently unavailable. In the present study, we speculate on how lung microbiota might interfere with acute and chronic infections by focusing exemplarily on the obligate intracellular C. pneumoniae. Furthermore, we consider changes in the gut microbiota as an additional player in the control of lung infections, especially in view the increasing evidence suggesting the involvement of the gut microbiota in various immunological processes throughout the human body.

Three CoA Transferases Involved in the Production of Short Chain Fatty Acids in Porphyromonas gingivalis

Butyryl-CoA:acetate CoA transferase, which produces butyrate and acetyl-CoA from butyryl-CoA and acetate, is responsible for the final step of butyrate production in bacteria. This study demonstrates that in the periodontopathogenic bacterium Porphyromonas gingivalis this reaction is not catalyzed by PGN_1171, previously annotated as butyryl-CoA:acetate CoA transferase, but by three distinct CoA transferases, PGN_0725, PGN_1341, and PGN_1888. Gas chromatography/mass spectrometry (GC-MS) and spectrophotometric analyses were performed using crude enzyme extracts from deletion mutant strains and purified recombinant proteins. The experiments revealed that, in the presence of acetate, PGN_0725 preferentially utilized butyryl-CoA rather than propionyl-CoA. By contrast, this preference was reversed in PGN_1888. The only butyryl-CoA:acetate CoA transferase activity was observed in PGN_1341. Double reciprocal plots revealed that all the reactions catalyzed by these enzymes follow a ternary-complex mechanism, in contrast to previously characterized CoA transferases. GC-MS analysis to determine the concentrations of short chain fatty acids (SCFAs) in culture supernatants of P. gingivalis wild type and mutant strains revealed that PGN_0725 and PGN_1888 play a major role in the production of butyrate and propionate, respectively. Interestingly, a triple deletion mutant lacking PGN_0725, PGN_1341, and PGN_1888 produced low levels of SCFAs, suggesting that the microorganism contains CoA transferase(s) in addition to these three enzymes. Growth rates of the mutant strains were mostly slower than that of the wild type, indicating that many carbon compounds produced in the SCFA synthesis appear to be important for the biological activity of this microorganism.

Acyl-CoA reductase PGN_0723 utilizes succinyl-CoA to generate succinate semialdehyde in a butyrate-producing pathway of Porphyromonas gingivalis

The molecular basis of butyrate production in Porphyromonas gingivalis has not been fully elucidated, even though butyrate, a short chain fatty acid (SCFA), can exert both beneficial and harmful effects on a mammalian host. A database search showed that the amino acid sequence of PGN_0723 protein was 50.6% identical with CoA-dependent succinate semialdehyde dehydrogenase (SSADH) in Clostridium kluyveri. By contrast, the protein has limited identity (19.1%) with CoA-independent SSADH in Escherichia coli. Compared with the wild type, growth speed, and final turbidity were lower in the PGN_0723 deletion strain that was constructed by replacing the PGN_0723 gene with an erythromycin resistance cassette. Gas chromatography mass spectrometry revealed the supernatant concentrations of the SCFAs butyrate, isobutyrate, and isovalerate, but not propionate, in the PGN_0723 deletion strain were also lower than those in the wild type. The wild-type phenotype was restored in a complemented strain. We cloned the PGN_0723 gene, purified the recombinant protein, and computationally constructed its three-dimensional model. A colorimetric assay and liquid chromatography-tandem mass spectrometry analysis demonstrated that the recombinant PGN_0723 produces succinate semialdehyde, which is an intermediate in the P. gingivalis butyrate synthesis pathway, not from succinate but from succinyl-CoA in the presence of NAD(P)H via a ping-pong bi-bi mechanism. Asn110Ala and Cys239Ala mutations resulted in a significant loss of the CoA-dependent PGN_0723 enzymatic activity. The study provides new insights into butyrate production, which constitutes a virulence factor in P. gingivalis.