An overview of the alpha-, beta- and gamma-carbonic anhydrases from Bacteria: can bacterial carbonic anhydrases shed new light on evolution of bacteria?

Cloning, expression, and purification of an α-carbonic anhydrase from Toxoplasma gondii to unveil its kinetic parameters and anion inhibition profile

Toxoplasmosis, induced by the intracellular parasite Toxoplasma gondii, holds considerable implications for global health. While treatment options primarily focusing on folate pathway enzymes have notable limitations, current research endeavours concentrate on pinpointing specific metabolic pathways vital for parasite survival. Carbonic anhydrases (CAs, EC 4.2.1.1) have emerged as potential drug targets due to their role in fundamental reactions critical for various protozoan metabolic processes. Within T. gondii, the Carbonic Anhydrase-Related Protein (TgCA_RP) plays a pivotal role in rhoptry biogenesis. Notably, α-CA (TcCA) from another protozoan, Trypanosoma cruzi, exhibited considerable susceptibility to classical CA inhibitors (CAIs) such as anions, sulphonamides, thiols, and hydroxamates. Here, the recombinant DNA technology was employed to synthesise and clone the identified gene in the T. gondii genome, which encodes an α-CA protein (Tg_CA), with the purpose of heterologously overexpressing its corresponding protein. Tg_CA kinetic constants were determined, and its inhibition patterns explored with inorganic metal-complexing compounds, which are relevant for rational compound design. The significance of this study lies in the potential development of innovative therapeutic strategies that disrupt the vital metabolic pathways crucial for T. gondii survival and virulence. This research may lead to the development of targeted treatments, offering new approaches to manage toxoplasmosis.

A comprehensive investigation of the anion inhibition profile of a β-carbonic anhydrase from Acinetobacter baumannii for crafting innovative antimicrobial treatments

This study refers to the intricate world of Acinetobacter baumannii, a resilient pathogenic bacterium notorious for its propensity at antibiotic resistance in nosocomial infections. Expanding upon previous findings that emphasised the bifunctional enzyme PaaY, revealing unexpected γ-carbonic anhydrase (CA) activity, our research focuses on a different class of CA identified within the A. baumannii genome, the β-CA, designated as 𝛽-AbauCA (also indicated as CanB), which plays a crucial role in the resistance mechanism mediated by AmpC beta-lactamase. Here, we cloned, expressed, and purified the recombinant 𝛽-AbauCA, unveiling its distinctive kinetic properties and inhibition profile with inorganic anions (classical CA inhibitors). The exploration of 𝛽-AbauCA not only enhances our understanding of the CA repertoire of A. baumannii but also establishes a foundation for targeted therapeutic interventions against this resilient pathogen, promising advancements in combating its adaptability and antibiotic resistance.

Physiological modeling of the metaverse of the Mycobacterium tuberculosis β-CA inhibition mechanism

Tuberculosis (TB) is an infectious disease that primarily affects the lungs of humans and accounts for Mycobacterium tuberculosis (Mtb) bacteria as the etiologic agent. In this study, we introduce a computational framework designed to identify the important chemical features crucial for the effective inhibition of Mtb β-CAs. Through applying a mechanistic model, we elucidated the essential features pivotal for robust inhibition. Using this model, we engineered molecules that exhibit potent inhibitory activity and introduce relevant novel chemistry. The designed molecules were prioritized for synthesis based on their predicted pKi values via the QSAR (Quantitative Structure-Activity Relationship) model. All the rationally designed and synthesized compounds were evaluated in vitro against different carbonic anhydrase isoforms expressed from the pathogen Mtb; moreover, the off-target and widely human-expressed CA I and II were also evaluated. Among the reported derivatives, 2, 4, and 5 demonstrated the most valuable in vitro activity, resulting in promising candidates for the treatment of TB infection. All the synthesized molecules exhibited favorable pharmacokinetic and toxicological profiles based on in silico predictions. Docking analysis confirmed that the zinc-binding groups bind effectively into the catalytic triad of the Mtb β-Cas, supporting the in vitro outcomes with these binding interactions. Furthermore, molecules with good prediction accuracies according to previously established mechanistic and QSAR models were utilized to delve deeper into the realm of systems biology to understand their mechanism in combating tuberculotic pathogenesis. The results pointed to the key involvement of the compounds in modulating immune responses via NF-κβ1, SRC kinase, and TNF-α to modulate granuloma formation and clearance via T cells. This dual action, in which the pathogen's enzyme is inhibited while modulating the human immune machinery, represents a paradigm shift toward more effective and comprehensive treatment approaches for combating tuberculosis.

Characterization of two carbonic anhydrase isoforms in the pulmonate snail (Lymnaea Stagnalis) and their involvement in Molluskan calcification

Calcifying organisms are suffering from negative impacts induced by climate change, such as CO2-induced acidification, which may impair external calcified structures. Freshwater mollusks have the potential to suffer more from CO2-induced acidification than marine calcifiers due to the lower buffering capacity of many freshwater systems. One of the most important enzymes contributing to the biomineralization reaction is carbonic anhydrase (CA), which catalyzes the reversible conversion of CO2 to bicarbonate, the major carbon source of the calcareous structure in calcifiers. In this study we characterized two α-CA isoforms (LsCA1 and LsCA4) from the freshwater snail Lymnaea stagnalis using a combination of gene sequencing, gene expression, phylogenetic analysis and biochemical assays. Both CA isoforms demonstrated high expression levels in the mantle tissue, the major site for biomineralization. Furthermore, expression of LsCA4 during development parallels shell formation. The primary protein structure analysis, active site configuration and the catalytic activity of LsCA4 together suggest that the LsCA4 is embedded in the apical and basolateral membranes of mantle cells; while LsCA1 is proposed to be cytosolic and might play an important role in acid-base regulation. These findings of LsCA isoforms form a strong basis for a more detailed physiological understanding of the effects of elevated CO2 on calcification in freshwater mollusks.

Benzothiazole derivatives in the design of antitumor agents

Benzothiazoles are a class of heterocycles with multiple applications as anticancer, antibiotic, antiviral, and anti-inflammatory agents. Benzothiazole is a privileged scaffold in drug discovery programs for modulating a variety of biological functions. This review focuses on the design and synthesis of new benzothiazole derivatives targeting hypoxic tumors. Cancer is a major health problem, being among the leading causes of death. Tumor-hypoxic areas promote proliferation, malignancy, and resistance to drug treatment, leading to the dysregulation of key signaling pathways that involve drug targets such as vascular endothelial growth factor, epidermal growth factor receptor, hepatocyte growth factor receptor, dual-specificity protein kinase, cyclin-dependent protein kinases, casein kinase 2, Rho-related coil formation protein kinase, tunica interna endothelial cell kinase, cyclooxygenase-2, adenosine kinase, lysophosphatidic acid acyltransferases, stearoyl-CoA desaturase, peroxisome proliferator-activated receptors, thioredoxin, heat shock proteins, and carbonic anhydrase IX/XII. In turn, they regulate angiogenesis, proliferation, differentiation, and cell survival, controlling the cell cycle, inflammation, the immune system, and metabolic alterations. A wide diversity of benzothiazoles were reported over the last years to interfere with various proteins involved in tumorigenesis and, more specifically, in hypoxic tumors. Many hypoxic targets are overexpressed as a result of the hypoxia-inducible factor activation cascade and may not be present in normal tissues, providing a potential strategy for selectively targeting hypoxic cancers.

Bacterial γ-carbonic anhydrases

Carbonic anhydrases (CAs) are a ubiquitous family of zinc metalloenzymes that catalyze the reversible hydration of carbon dioxide to bicarbonate and protons, playing pivotal roles in a variety of biological processes including respiration, calcification, acid-base balance, and CO2 fixation. Recent studies have expanded the understanding of CAs, particularly the γ-class from diverse biological sources such as pathogenic bacteria, extremophiles, and halophiles, revealing their unique structural adaptations and functional mechanisms that enable operation under extreme environmental conditions. This chapter discusses the comprehensive catalytic mechanism and structural insights from X-ray crystallography studies, highlighting the molecular adaptations that confer stability and activity to these enzymes in harsh environments. It also explores the modulation mechanism of these enzymes, detailing how different modulators interact with the active site of γ-CAs. Comparative analyzes with other CA classes elucidate the evolutionary trajectories and functional diversifications of these enzymes. The synthesis of this knowledge not only sheds light on the fundamental aspects of CA biology but also opens new avenues for therapeutic and industrial applications, particularly in designing targeted inhibitors for pathogenic bacteria and developing biocatalysts for industrial processes under extreme conditions. The continuous advancement in structural biology promises further insights into this enzyme family, potentially leading to novel applications in medical and environmental biotechnology.

Bacterial β-carbonic anhydrases

β-Carbonic anhydrases (β-CA; EC 4.2.1.1) are widespread zinc metalloenzymes which catalyze the interconversion of carbon dioxide and bicarbonate. They have been isolated in many pathogenic and non-pathogenic bacteria where they are involved in multiple roles, often related to their growth and survival. β-CAs are structurally distant from the CAs of other classes. In the active site, located at the interface of a fundamental dimer, the zinc ion is coordinated to two cysteines and one histidine. β-CAs have been divided in two subgroups depending on the nature of the fourth ligand on the zinc ion: class I have a zinc open configuration with a hydroxide ion completing the metal coordination, which is the catalytically active species in the mechanism proposed for the β-CAs similar to the well-known of α-CAs, while in class II an Asp residue substitute the hydroxide. This latter active site configuration has been showed to be typical of an inactive form at pH below 8. An Asp-Arg dyad is thought to play a key role in the pH-induced catalytic switch regulating the opening and closing of the active site in class II β-CAs, by displacing the zinc-bound solvent molecule. An allosteric site well-suited for bicarbonate stabilizes the inactive form. This bicarbonate binding site is composed by a triad of well conserved residues, strictly connected to the coordination state of the zinc ion. Moreover, the escort site is a promiscuous site for a variety of ligands, including bicarbonate, at the dimer interface, which may be the route for bicarbonate to the allosteric site.

Bacterial α-CAs: a biochemical and structural overview

Carbonic anhydrases belonging to the α-class are widely distributed in bacterial species. These enzymes have been isolated from bacteria with completely different characteristics including both Gram-negative and Gram-positive strains. α-CAs show a considerable similarity when comparing the biochemical, kinetic and structural features, with only small differences which reflect the diverse role these enzymes play in Nature. In this chapter, we provide a comprehensive overview on bacterial α-CA data, with a highlight to their potential biomedical and biotechnological applications.

Sulfonamide inhibitors of bacterial carbonic anhydrases

The increasing prevalence of antibiotic-resistant bacteria necessitates the exploration of novel therapeutic targets. Bacterial carbonic anhydrases (CAs) have been known for decades, but only in the past ten years they have garnered significant interest as drug targets to develop antibiotics having a diverse mechanism of action compared to the clinically used drugs. Significant progress has been made in the field in the past three years, with the validation in vivo of CAs from Neisseria gonorrhoeae, and vancomycin-resistant enterococci as antibiotic targets. This chapter compiles the state-of-the-art research on sulfonamide derivatives described as inhibitors of all known bacterial CAs. A section delves into the mechanisms of action of sulfonamide compounds with the CA classes identified in pathogenic bacteria, specifically α, β, and γ classes. Therefore, the inhibitory profiling of the bacterial CAs with classical and clinically used sulfonamide compounds is reported and analyzed. Another section covers various other series of sulfonamide CA inhibitors studied for the development of new antibiotics. By synthesizing current research findings, this chapter highlights the potential of sulfonamide inhibitors as a novel class of antibacterial agents and paves the way for future drug design strategies.

Challenges for developing bacterial CA inhibitors as novel antibiotics

Acetazolamide, methazolamide, ethoxzolamide and dorzolamide, classical sulfonamide carbonic anhydrase (CA) inhibitors (CAIs) designed for targeting human enzymes, were also shown to effectively inhibit bacterial CAs and were proposed for repurposing as antibacterial agents against several infective agents. CAs belonging to the α-, β- and/or γ-classes from pathogens such as Helicobacter pylori, Neisseria gonorrhoeae, vacomycin resistant enterococci (VRE), Vibrio cholerae, Mycobacterium tuberculosis, Pseudomonas aeruginosa and other bacteria were considered as drug targets for which several classes of potent inhibitors have been developed. Treatment of some of these pathogens with various classes of such CAIs led to an impairment of the bacterial growth, reduced virulence and for drug resistant bacteria, a resensitization to clinically used antibiotics. Here I will discuss the strategies and challenges for obtaining CAIs with enhanced selectivity for inhibiting bacterial versus human enzymes, which may constitute an important weapon for addressing the drug resistance to β-lactams and other clinically used antibiotics.

Exploring rhodanine linked enamine-carbohydrazide derivatives as mycobacterial carbonic anhydrase inhibitors: Design, synthesis, biological evaluation, and molecular docking studies

With the rise of multidrug-resistant tuberculosis, the imperative for an alternative and superior treatment regimen, incorporating novel mechanisms of action, has become crucial. In pursuit of this goal, we have developed and synthesized a new series of rhodanine-linked enamine-carbohydrazide derivatives, exploring their potential as inhibitors of mycobacterial carbonic anhydrase. The findings reveal their efficacy, displaying notable selectivity toward the mycobacterial carbonic anhydrase 2 (mtCA 2) enzyme. While exhibiting moderate activity against human carbonic anhydrase isoforms, this series demonstrates promising selectivity, positioning these compounds as potential antitubercular agents. Compound 6d was the best one from the series with a Ki value of 9.5 µM toward mtCA 2. Most of the compounds displayed moderate to good inhibition against the Mtb H37Rv strain; compound 11k showed a minimum inhibitory concentration of 1 µg/mL. Molecular docking studies revealed that compounds 6d and 11k show metal coordination with the zinc ion, like classical CA inhibitors.

Microbially induced calcium carbonate precipitation through CO2 sequestration via an engineered Bacillus subtilis

BACKGROUND

Microbially induced calcium carbonate precipitation has been extensively researched for geoengineering applications as well as diverse uses within the built environment. Bacteria play a crucial role in producing calcium carbonate minerals, via enzymes including carbonic anhydrase-an enzyme with the capability to hydrolyse CO2, commonly employed in carbon capture systems. This study describes previously uncharacterised carbonic anhydrase enzyme sequences capable of sequestering CO2 and subsequentially generating CaCO3 biominerals and suggests a route to produce carbon negative cementitious materials for the construction industry.

RESULTS

Here, Bacillus subtilis was engineered to recombinantly express previously uncharacterised carbonic anhydrase enzymes from Bacillus megaterium and used as a whole cell catalyst allowing this novel bacterium to sequester CO2 and convert it to calcium carbonate. A significant decrease in CO2 was observed from 3800 PPM to 820 PPM upon induction of carbonic anhydrase and minerals recovered from these experiments were identified as calcite and vaterite using X-ray diffraction. Further experiments mixed the use of this enzyme (as a cell free extract) with Sporosarcina pasteurii to increase mineral production whilst maintaining a comparable level of CO2 sequestration.

CONCLUSION

Recombinantly produced carbonic anhydrase successfully sequestered CO2 and converted it into calcium carbonate minerals using an engineered microbial system. Through this approach, a process to manufacture cementitious materials with carbon sequestration ability could be developed.

Enterococci carbonic anhydrase inhibition

Carbonic anhydrase metalloenzymes are encoded in genomes throughout all kingdoms of life with a conserved function catalyzing the reversible conversion of CO2 to bicarbonate. Carbonic anhydrases have been well-investigated in humans, but are still relatively understudied in bacterial organisms, including Enterococci. Studies over the past decade have presented bacterial carbonic anhydrases as potential drug targets, with some chemical scaffolds potently inhibiting the Enterococcus carbonic anhydrases in vitro and displaying antimicrobial efficacy against Enterococcus organisms. While carbonic anhydrases in Enterococci still have much to be explored, hypotheses may be drawn from similar Gram-positive organisms for which known information exists about carbonic anhydrase function and relevance. Within this chapter is reported information and rational hypotheses regarding the subcellar locations, potential physiological roles, essentiality, structures, and kinetics of carbonic anhydrases in Enterococci.

Neisseria gonorrhoeae carbonic anhydrase inhibition

Carbonic anhydrases (CAs) are ubiquitous enzymes that are found in all kingdoms of life. Though different classes of CAs vary in their roles and structures, their primary function is to catalyze the reaction between carbon dioxide and water to produce bicarbonate and a proton. Neisseria gonorrhoeae encodes for three distinct CAs (NgCAs) from three different families: an α-, a β-, and a γ-isoform. This chapter details the differences between the three NgCAs, summarizing their subcellular locations, roles, essentiality, structures, and enzyme kinetics. These bacterial enzymes have the potential to be drug targets; thus, previous studies have investigated the inhibition of NgCAs-primarily the α-isoform. Therefore, the classes of inhibitors that have been shown to bind to the NgCAs will be discussed as well. These classes include traditional CA inhibitors, such as sulfonamides, phenols, and coumarins, as well as non-traditional inhibitors including anions and thiocarbamates.

Carbonic anhydrases in bacterial pathogens

Carbonic anhydrases (CAs) catalyze the reversable hydration of carbon dioxide to bicarbonate placing them into the core of the biochemical carbon cycle. Due to the fundamental importance of their function, they evolved independently into eight classes, three of which have been recently discovered. Most research on CAs has focused on their representatives in eukaryotic organisms, while prokaryotic CAs received significantly less attention. Nevertheless, prokaryotic CAs play a key role in the fundamental ability of the biosphere to acquire CO2 for photosynthesis and to decompose the organic matter back to CO2. They also contribute to a broad spectrum of processes in pathogenic bacteria, enhancing their ability to survive in a host and, therefore, present a promising target for developing antimicrobials. This review focuses on the distribution of CAs among bacterial pathogens and their importance in bacterial virulence and host-pathogen interactions.

Overview on bacterial carbonic anhydrase genetic families

Bacterial carbonic anhydrases (BCAs, EC 4.2.1.1) are indispensable enzymes in microbial physiology because they facilitate the hydration of carbon dioxide (CO2) to bicarbonate ions (HCO3-) and protons (H+), which are crucial for various metabolic processes and cellular homeostasis. Their involvement spans from metabolic pathways, such as photosynthesis, respiration, to organic compounds production, which are pivotal for bacterial growth and survival. This chapter elucidates the diversity of BCA genetic families, categorized into four distinct classes (α, β, γ, and ι), which may reflect bacterial adaptation to environmental niches and their metabolic demands. The diversity of BCAs is essential not only for understanding their physiological roles but also for exploring their potential in biotechnology. Knowledge of their diversity enables researchers to develop innovative biocatalysts for industrial applications, including carbon capture technologies to convert CO2 emissions into valuable products. Additionally, BCAs are relevant to biomedical research and drug development because of their involvement in bacterial pathogenesis and microbial survival within the host. Understanding the diversity and function of BCAs can aid in designing targeted therapeutics that interfere with bacterial metabolism and potentially reduce the risk of infections.

Bacterial ι-CAs

Recent research has identified a novel class of carbonic anhydrases (CAs), designated ι-CA, predominantly found in marine diatoms, eukaryotic algae, cyanobacteria, bacteria, and archaea genomes. This class has garnered attention owing to its unique biochemical properties and evolutionary significance. Through bioinformatic analyses, LCIP63, a protein initially annotated with an unknown function, was identified as a potential ι-CA in the marine diatom Thalassiosira pseudonana. Subsequent biochemical characterization revealed that LCIP63 has CA activity and its preference for manganese ions over zinc, indicative of evolutionary adaptation to marine environments. Further exploration of bacterial ι-CAs, exemplified by Burkholderia territorii ι-CA (BteCAι), demonstrated catalytic efficiency and sensitivity to sulfonamide and inorganic anion inhibitors, the classical CA inhibitors (CAIs). The classification of ι-CAs into two variant types based on their sequences, distinguished by the COG4875 and COG4337 domains, marks a significant advancement in our understanding of these enzymes. Structural analyses of COG4337 ι-CAs from eukaryotic microalgae and cyanobacteria thereafter revealed a distinctive structural arrangement and a novel catalytic mechanism involving specific residues facilitating CO2 hydration in the absence of metal ion cofactors, deviating from canonical CA behavior. These findings underscore the biochemical diversity within the ι-CA class and highlight its potential as a target for novel antimicrobial agents. Overall, the elucidation of ι-CA properties and mechanisms advances our knowledge of carbon metabolism in diverse organisms and underscores the complexity of CA evolution and function.

Management of Neisseria gonorrhoeae infection: from drug resistance to drug repurposing

INTRODUCTION

Neisseria gonorrhoeae is a common sexually transmitted disease connected with extensive drug resistance to many antibiotics. Presently, only expanded spectrum cephalosporins (ceftriaxone and cefixime) and azithromycin remain useful for its management.

AREAS COVERED

New chemotypes for the classical antibiotic drug target gyrase/topoisomerase IV afforded inhibitors with potent binding to these enzymes, with an inhibition mechanism distinct from that of fluoroquinolones, and thus less prone to mutations. The α-carbonic anhydrase from the genome of this bacterium (NgCAα) was also validated as an antibacterial target.

EXPERT OPINION

By exploiting different subunits from the gyrase/topoisomerase IV as well as new chemotypes, two new antibiotics reached Phase II/III clinical trials, zoliflodacin and gepotidacin. They possess a novel inhibition mechanism, binding in distinct parts of the enzyme compared to the fluoroquinolones. Other chemotypes with inhibitory activity in these enzymes were also reported. NgCAα inhibitors belonging to a variety of classes were obtained, with several sulfonamides showing MIC values in the range of 0.25-4 µg/mL and significant activity in animal models of this infection. Acetazolamide and similar CA inhibitors might thus be repurposed as antiinfectives. The scientific/patent literature has been searched for on PubMed, ScienceDirect, Espacenet, and PatentGuru, from 2016 to 2024.

Carbonic anhydrase and bacterial metabolism: a chance for antibacterial drug discovery

INTRODUCTION

Carbonic anhydrases (CAs, EC 4.2.1.1) play a pivotal role in the regulation of carbon dioxide , bicarbonate, and hydrogen ions within bacterial cells, ensuring pH homeostasis and facilitating energy production. We conducted a systematic literature search (PubMed, Web of Science, and Google Scholar) to examine the intricate interplay between CAs and bacterial metabolism, revealing the potential of CA inhibitors (CAIs) as innovative therapeutic agents against pathogenic bacteria.

AREA COVERED

Inhibition of bacterial CAs was explored in various pathogens, emphasizing the CA roles in microbial virulence, survival, and adaptability. Escherichia coli, a valid and convenient model microorganism, was recently used to investigate the effects of acetazolamide (AAZ) on the bacterial life cycle. Furthermore, the effectiveness of CAIs against pathogenic bacteria has been further substantiated for Vancomycin-Resistant Enterococci (VRE) and antibiotic-resistant Neisseria gonorrhoeae strains.

EXPERT OPINION

CAIs target bacterial metabolic pathways, offering alternatives to conventional therapies. They hold promise against drug-resistant microorganisms such as VRE and N. gonorrhoeae strains. CAIs offer promising avenues for addressing antibiotic resistance and underscore their potential as novel antibacterial agents. Recognizing the central role of CAs in bacterial growth and pathogenicity will pave the way for innovative infection control and treatment strategies possibly also for other antibiotic resistant species.

Alpha Carbonic Anhydrase from Nitratiruptor tergarcus Engineered for Increased Activity and Thermostability

The development of carbon capture and storage technologies has resulted in a rising interest in the use of carbonic anhydrases (CAs) for CO2 fixation at elevated temperatures. In this study, we chose to rationally engineer the α-CA (NtCA) from the thermophilic bacterium Nitratiruptor tergarcus, which has been previously suggested to be thermostable by in silico studies. Using a combination of analyses with the DEEPDDG software and available structural knowledge, we selected residues in three regions, namely, the catalytic pocket, the dimeric interface and the surface, in order to increase thermostability and CO2 hydration activity. A total of 13 specific mutations, affecting seven amino acids, were assessed. Single, double and quadruple mutants were produced in Escherichia coli and analyzed. The best-performing mutations that led to improvements in both activity and stability were D168K, a surface mutation, and R210L, a mutation in the dimeric interface. Apart from these, most mutants showed improved thermostability, with mutants R210K and N88K_R210L showing substantial improvements in activity, up to 11-fold. Molecular dynamics simulations, focusing particularly on residue fluctuations, conformational changes and hydrogen bond analysis, elucidated the structural changes imposed by the mutations. Successful engineering of NtCA provided valuable lessons for further engineering of α-CAs.

Characteristics of cold-adapted carbonic anhydrase and efficient carbon dioxide capture based on cell surface display technology

Carbonic anhydrase (CA) is currently under investigation because of its potential to capture CO2. A novel N-domain of ice nucleoproteins (INPN)-mediated surface display technique was developed to produce CA with low-temperature capture CO2 based on the mining and characterization of Colwellia sp. CA (CsCA) with cold-adapted enzyme structural features and catalytic properties. CsCA and INPN were effectively integrated into the outer membrane of the cell as fusion proteins. Throughout the display process, the integrity of the membrane of engineered bacteria BL21/INPN-CsCA was maintained. Notably, the study affirmed positive applicability, wherein 94 % activity persisted after 5 d at 15 °C, and 73 % of the activity was regained after 5 cycles of CO2 capture. BL21/INPN-CsCA displayed a high CO2 capture capacity of 52 mg of CaCO3/mg of whole-cell biocatalysts during CO2 mineralization at 25 °C. Therefore, the CsCA functional cell surface display technology could contribute significantly to environmentally friendly CO2 capture.

Biomedical applications of prokaryotic carbonic anhydrases: an update

INTRODUCTION

This review offers an updated perspective on the biomedical applications of prokaryotic carbonic anhydrases (CAs), emphasizing their potential as targets for drug development against antibiotic-resistant bacterial infections. A systematic review of literature from PubMed, Web of Science, and Google Scholar has been conducted to provide a comprehensive analysis.

AREA COVERED

It delves into the pivotal roles of prokaryotic CAs in bacterial metabolism and their distinctions from mammalian CAs. The review explores the diversity of CA classes in bacteria, discusses selective inhibitors targeting bacterial CAs, and explores their potential applications in biomedical research. Furthermore, it analyzes clinical trials investigating the efficacy of carbonic anhydrase inhibitors (CAIs) and patented approaches for developing antibacterial CAIs, highlighting their translational potential in creating innovative antibacterial agents.

EXPERT OPINION

Recent years have witnessed increased recognition of CA inhibition as a promising strategy against bacterial infections. Challenges persist in achieving selectivity over human isoforms and optimizing therapeutic efficacy. Structural biology techniques provide insights into unique active site architectures, guiding selective inhibitor design. The review underscores the importance of interdisciplinary collaborations, innovative drug delivery systems, and advanced drug discovery approaches in unlocking the full therapeutic potential of prokaryotic CA inhibitors. It emphasizes the significance of these efforts in addressing antibiotic resistance and improving patient outcomes.

Discovery of water-soluble semicarbazide-containing sulfonamide derivatives possessing favorable anti-glaucoma effect in vivo and drug-like properties

In order to obtain topical and non-irritating anti-glaucoma drugs, novel semicarbazide-containing sulfonamide derivatives were designed and synthetized by sugar tail method in this study. The hydrophilic monosaccharides were expected to form interaction with the hydrophilic site of hCA II meanwhile the linker semicarbazides are used to further enhance water solubility, and more importantly, regulate the pH values of the target compounds in aqueous solution. First, all target compounds were synthesized and evaluated for their CA inhibitory activities. The results showed our target compounds demonstrated comparable activity to the positive control drug acetazolamide. The best derivative 11d exhibits an IC50 value of 14 nM for hCA II and 2086-fold selectivity over CA I. Subsequently, physicochemical properties study showed that the target compounds displayed very good water solubility (up to 3 %) and neutral pH value in solutions. Meanwhile, the artificial membrane permeability assay was performed to verify that the target compound could also pass through the membrane structure despite their strong water solubility. In the glaucomatous rabbit eye model, the applied topically representative compounds showed strongly lowered intraocular pressure (IOP), as 1 % or 2 % water solutions. Subsequent drug-like evaluation showed our target compounds possessed low hemolysis effect and low cytotoxicity toward human corneal epithelial cell line. Also, it was not found that these target compounds had significant inhibition of hERG and CYP. In addition, these novel analogs also displayed good liver microsomal metabolic stability and plasma stability. Finally, docking studies provided the rational binding modes of representative compounds in complex with hCA II. Taken together, these results suggested that compound 11d may be a promising hCA II inhibitor deserving further development.

Sulfonamide derivatives with benzothiazole scaffold: Synthesis and carbonic anhydrase I-II inhibition properties

The secondary sulfonamide derivatives containing benzothiazole scaffold (1-10) were synthesized to determine their inhibition properties on two physiologically essential human carbonic anhydrases isoforms (hCAs, EC, 4.2.1.1), hCA I, and hCA II. The inhibitory effects of the compounds on hCA I and hCA II isoenzymes were investigated by comparing their IC50 and Ki values. The Ki values of compounds (1-10) against hCA I and hCA II are in the range of 0.052 ± 0.022-0.971 ± 0.280 and 0.025 ± 0.010-0.682 ± 0.335, respectively. Some of these inhibited the enzyme more effectively than the standard drug, acetazolamide. In particular, compounds 5 and 4 were found to be most effective on hCA I and hCA II.

pH-Dependent Structure and Dynamics of the Catalytic Domains of Human Carbonic Anhydrase II and IX

Extensive computer simulation studies have been carried out to probe the pH-dependent structure and dynamics of the two most efficient isoenzymes II and IX of human carbonic anhydrase (HCA) that control the pH in the human body. The equilibrium structure and hydration of their catalytic domains are found to be largely unaffected by the variation of pH in the range studied, in close agreement with the known experimental results. In contrast, a significant effect of the change in pH is observed for the first time on the local electrostatic potential of the active site walls and the dynamics of active site water molecules. We also report for the first time the free energy and kinetics of coupled fluctuations of orientation and protonation states of the well-known His-mediated proton shuttle (His-64) in both isozymes at pH 7 and 8. The transitions between different tautomers of in or out conformations of His-64 side chain range between 109 and 106 s-1 depending on pH. Possible implications of these results on conformation-dependent pKa of His-64 side chain and its role in driving the catalysis toward hydration of CO2 or dehydration of HCO3- with varying pH are discussed.

Novel thiazolone-benzenesulphonamide inhibitors of human and bacterial carbonic anhydrases

A small library of novel thiazolone-benzenesulphonamides has been prepared and evaluated for their ability to inhibit three human cytosolic carbonic anhydrases (hCA I, hCA II, and hCA VII) and three bacterial carbonic anhydrases (MscCAβ, StCA1, and StCA2). All investigated hCAs were inhibited by the prepared compounds 4a-4j in the low nanomolar range. These compounds were effective hCA I inhibitors (K_Is of 31.5-637.3 nM) and excellent hCA II (K_Is in the range of 1.3-13.7 nM) and hCA VII inhibitors (K_Is in the range of 0.9-14.6 nM). The most active analog in the series, 4-((4-oxo-5-propyl-4,5-dihydrothiazol-2-yl)amino)benzenesulphonamide 4d, strongly inhibited bacterial MscCAβ, with K_I of 73.6 nM, considerably better than AAZ (K_I of 625 nM). The tested compounds displayed medium inhibitory potency against StCA1 (K_Is of 69.2-163.3 nM) when compared to the standard drug (K_I of 59 nM). However, StCA2 was poorly inhibited by the sulphonamides reported here, with K_Is in the micromolar range between 275.2 and 4875.0 nM.

Discovery of the first-in-class potent and isoform-selective human carbonic anhydrase III inhibitors

Considering the unrecognised physio-pathological role of human carbonic anhydrase III (hCA III), a structure-based drug design was set up to identify the first-in-class potent and selective inhibitors of this neglected isoform. hCA III targeting was planned considering a unique feature of its active site among the other hCA isoforms, i.e. the Leu198/Phe198 substitution which interferes with the binding of aromatic/heterocyclic sulfonamides and other inhibitors. Thus, new aliphatic primary sulfonamides possessing long and flexible (CH2)nSO2NH2 moieties were designed to coordinate the zinc(II) ion, bypassing the bulky Phe198 residue. They incorporate 1,2,3-triazole linkers which connect the tail moieties to the sulfonamide head, enhancing thus the contacts at the active site entrance. Some of these compounds act as nanomolar and selective inhibitors of hCA III over other isoforms. Docking/molecular dynamics simulations were used to investigate ligand/target interactions for these sulfonamides which might improve our understanding of the physio-pathological roles of hCA III.

Selected strategies to fight pathogenic bacteria

Natural products and analogues are a source of antibacterial drug discovery. Considering drug resistance levels emerging for antibiotics, identification of bacterial metalloenzymes and the synthesis of selective inhibitors are interesting for antibacterial agent development. Peptide nucleic acids are attractive antisense and antigene agents representing a novel strategy to target pathogens due to their unique mechanism of action. Antisense inhibition and development of antisense peptide nucleic acids is a new approach to antibacterial agents. Due to the increased resistance of biofilms to antibiotics, alternative therapeutic options are necessary. To develop antimicrobial strategies, optimised in vitro and in vivo models are needed. In vivo models to study biofilm-related respiratory infections, device-related infections: ventilator-associated pneumonia, tissue-related infections: chronic infection models based on alginate or agar beads, methods to battle biofilm-related infections are discussed. Drug delivery in case of antibacterials often is a serious issue therefore this review includes overview of drug delivery nanosystems.

Dentine biomodification by sulphonamides pre-treatment: bond strength, proteolytic inhibition, and antimicrobial activity

We evaluated the effects of dentine biomodification after pre-treatment with two sulphonamide carbonic anhydrase inhibitors (CAIs) of the N-[4-sulphamoylphenethylcarbamoyl]benzenesulphonamide type, investigating matrix metalloproteases activity, resin-dentine micro tensile bond strength, dentine surface wettability, and antimicrobial activities. Ninety-five sound-extracted human molars were selected for the study. Inhibitory effects were evaluated by gelatinase and collagenase activity tests and collagen degradation FT-IR spectroscopic analysis. Pre-treatment with the two CAIs kept the micro tensile values after 12 months of storage (32.23 ± 5.95) and cariogenic challenge (34.13 ± 2.71) similar to the initial, pre-treatment values (33.56 ± 4.34). A decreased Streptococcus mutans biofilm formation on dentine surfaces and antibacterial activity against planktonic bacteria were observed after CAI treatment. Dentine pre-treatment with sulphonamide CAIs maintained adhesion strength stability, allowed better dentine wettability, maintained matrix collagen, and showed anti-S. mutans activity.

Cloning, characterization, and inhibition of the novel β-carbonic anhydrase from parasitic blood fluke, Schistosoma mansoni

Schistosoma mansoni is an intestinal parasite with one β-class carbonic anhydrase, SmaBCA. We report the sequence enhancing, production, catalytic activity, and inhibition results of the recombinant SmaBCA. It showed significant catalytic activity on CO₂ hydration in vitro with k_cat 1.38 × 10⁵ s^-1 and k_cat/K_m 2.33 × 10⁷ M^-1 s^-1. Several sulphonamide inhibitors, from which many are clinically used, showed submicromolar or nanomolar inhibitory effects on SmaBCA. The most efficient inhibitor with a K_I of 43.8 nM was 4-(2-amino-pyrimidine-4-yl)-benzenesulfonamide. Other effective inhibitors with K_Is in the range of 79.4-95.9 nM were benzolamide, brinzolamide, topiramate, dorzolamide, saccharin, epacadostat, celecoxib, and famotidine. The other tested compounds showed at least micromolar range inhibition against SmaBCA. Our results introduce SmaBCA as a novel target for drug development against schistosomiasis, a highly prevalent parasitic disease.

Antihistamines, phenothiazine-based antipsychotics, and tricyclic antidepressants potently activate pharmacologically relevant human carbonic anhydrase isoforms II and VII

Carbonic anhydrases (CAs) are important regulators of pH homeostasis and participate in many physiological and pathological processes. CA activators (CAAs) are becoming increasingly important in the biomedical field since enhancing CA activity may have beneficial effects at neurological level. Here, we investigate selected antihistamines, phenothiazine-based antipsychotics, and tricyclic antidepressants (TCAs) as potential activators of human CAs I, II, IV, and VII. Our findings indicate that these compounds are more effective at activating hCA II and VII compared to hCA I and IV. Overall, hCA VII was the most efficiently activated isoform, particularly by phenothiazines and TCAs. This is especially relevant since hCA VII is the most abundant isoform in the central nervous system (CNS) and is implicated in neuronal signalling and bicarbonate balance regulation. This study offers additional insights into the pharmacological profiles of clinically employed drugs and sets the ground for the development of novel optimised CAAs.

Carbonic anhydrase versatility: from pH regulation to CO2 sensing and metabolism

While the carbonic anhydrase (CA, EC 4.2.1.1) superfamily of enzymes has been described primarily as involved only in pH regulation for decades, it also has many other important functions. CO2, bicarbonate, and protons, the physiological substrates of CA, are indeed the main buffering system in organisms belonging to all life kingdoms; however, in the last period, relevant progress has been made in the direction of elucidating the involvement of the eight genetically distinct CA families in chemical sensing, metabolism, and several other crucial physiological processes. Interference with CA activity, both by inhibiting and activating these enzymes, has thus led to novel applications for CA inhibitors and activators in the field of innovative biomedicine and environment and health. In this perspective article, I will discuss the recent advances which have allowed for a deeper understanding of the biochemistry of these versatile enzymes and various applications of their modulators of activity.

Targeting carbonic anhydrases for the management of hypoxic metastatic tumors

INTRODUCTION

Several isoforms of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) are connected with tumorigenesis. Hypoxic tumors overexpress CA IX and XII as a consequence of HIF activation cascade, being involved in pH regulation, metabolism, and metastases formation. Other isoforms (CA I, II, III, IV) were also reported to be present in some tumors.

AREAS COVERED

Some CA isoforms are biomarkers for disease progression or response to therapy. Inhibitors, antibodies, and other procedures for targeting these enzymes for the treatment of tumors/metastases are discussed. Sulfonamides and coumarins represent the most investigated classes of inhibitors, but carboxylates, selenium, and tellurium-containing inhibitors were also investigated. Hybrid drugs of CA inhibitors with other antitumor agents for multitargeted therapy were reported.

EXPERT OPINION

Targeting CAs present in solid or hematological tumors with selective, targeted inhibitors is a validated approach, which has been consolidated in the last years. A host of new preclinical data and several clinical trials of antibodies and small-molecule inhibitors are ongoing, which connected with the large number of new chemotypes/procedures discovered to be effective, may lead to a breakthrough in this therapeutic area. The scientific/patent literature has been searched for on PubMed, ScienceDirect, Espacenet, and PatentGuru, from 2018 to 2023.

Potent and selective carbonic anhydrase inhibition activities of pyrazolones bearing benzenesulfonamides

This research introduces a series of fourteen 4-aryl-hydrazonopyrazolone sulfonamide derivatives, denoted as 3(a-g) and 4(a-g), which encompass various aromatic substitutions. The aim was to assess the inhibitory potential of these compounds against four significant isoforms, including the cytosolic isoforms hCA I and II, as well as the tumor-associated membrane-bound isoforms hCA IX and XII. Most of the tested compounds exhibited substantial inhibition against the tumor-associated isoform hCA IX, with Ki values spanning from 1.1 to 158.2 nM. Notably, compounds 3e and 3g showed particularly strong inhibitory activity against the tumor-associated membrane-bound isoforms, hCA IX and XII, while maintaining a high selectivity ratio over cytosolic off-target isoforms hCA I and II. This selectivity is vital due to the potential of hCA IX and hCA XII as drug targets for hypoxic tumors. In an effort to create novel analogs that exhibit enhanced carbonic anhydrase inhibitory activity and specificity, we investigated the structure-activity relationships of these compounds and provided a concise interpretation of our findings. Consequently, these compounds merit consideration for subsequent medicinal and pharmacological research, holding potential for developing novel therapeutic agents targeting specific isoforms in hypoxic tumors.

Ultrasensitive and rapid diagnostic tool for detection of Acanthamoeba castellanii

Acanthamoeba keratitis is a devastating infectious disease of the cornea caused by an opportunistic amoeba, Acanthamoeba castellanii. It is poorly recognized, and diagnostic delays can lead to irreversible damage to the vision. The gold standard for diagnosis has been a sample culture that lasts approximately 2 weeks. Nevertheless, the essence of time has led to the need for an accurate and fast technique to detect A. castellanii from a sample. We developed both traditional and quantitative real-time-PCR-based methods to detect A. castellanii in less than 3 hours and with the sensitivity of one amoeba. Diagnostic laboratories can select the best-suited method for their purposes from 2 comparable methods. The correct treatment can be initiated from the emergency room when the diagnosis has been made quickly within a few hours, hence saving the patient from long-term complications.

A simple yet multifaceted 90 years old, evergreen enzyme: Carbonic anhydrase, its inhibition and activation

Advances in the carbonic anhydrase (CA, EC 4.2.1.1) research over the last three decades are presented, with an emphasis on the deciphering of the activation mechanism, the development of isoform-selective inhibitors/ activators by the tail approach and their applications in the management of obesity, hypoxic tumors, neurological conditions, and as antiinfectives.

An overview of novel antimicrobial carbonic anhydrase inhibitors

INTRODUCTION

Four different genetic families of the enzyme carbonic anhydrase (CA, EC 4.2.1.1) are present in bacteria, α-, β-, γ- and ι-CAs. They play relevant functions related to CO2, HCO3-/H+ ions homeostasis, being involved in metabolic biosynthetic pathways, pH regulation, and represent virulence and survival factors for bacteria in various niches. Bacterial CAs started to be considered druggable targets in the last decade, as their inhibition impairs survival, growth, and virulence of these pathogens.

AREAS COVERED

Significant advances were registered in the last years for designing effective inhibitors of sulfonamide type for Helicobacter pylori α-CA, Neisseria gonorrhoeae α-CA, vacomycin-resistant enterococci (VRE) α- and γ-CAs, for which the in vivo validation has also been achieved. MIC-s in the range of 0.25-4.0 µg/mL for wild type and drug resistant N. gonorrhoeae strains, and of 0.007-2.0 µg/mL for VRE were observed for some 1,3,4-thiadiazole-2-sulfonamides, and acetazolamide was effective in gut decolonization from VRE.

EXPERT OPINION

Targeting bacterial CAs from other pathogens, among which Vibrio cholerae, Mycobacterium tuberculosis, Brucella suis, Salmonella enterica serovar Typhimurium, Legionella pneumophila, Porphyromonas gingivalis, Clostridium perfringens, Streptococcus mutans, Burkholderia pseudomallei, Francisella tularensis, Escherichia coli, Mammaliicoccus (Staphylococcus) sciuri, Pseudomonas aeruginosa, may lead to novel antibacterials devoid of drug resistance problems.

Genome Study of α-, β-, and γ-Carbonic Anhydrases from the Thermophilic Microbiome of Marine Hydrothermal Vent Ecosystems

Carbonic anhydrases (CAs) are metalloenzymes that can help organisms survive in hydrothermal vents by hydrating carbon dioxide (CO₂). In this study, we focus on alpha (α), beta (β), and gamma (γ) CAs, which are present in the thermophilic microbiome of marine hydrothermal vents. The coding genes of these enzymes can be transferred between hydrothermal-vent organisms via horizontal gene transfer (HGT), which is an important tool in natural biodiversity. We performed big data mining and bioinformatics studies on α-, β-, and γ-CA coding genes from the thermophilic microbiome of marine hydrothermal vents. The results showed a reasonable association between thermostable α-, β-, and γ-CAs in the microbial population of the hydrothermal vents. This relationship could be due to HGT. We found evidence of HGT of α- and β-CAs between Cycloclasticus sp., a symbiont of Bathymodiolus heckerae, and an endosymbiont of Riftia pachyptila via Integrons. Conversely, HGT of β-CA genes from the endosymbiont Tevnia jerichonana to the endosymbiont Riftia pachyptila was detected. In addition, Hydrogenovibrio crunogenus SP-41 contains a β-CA gene on genomic islands (GIs). This gene can be transferred by HGT to Hydrogenovibrio sp. MA2-6, a methanotrophic endosymbiont of Bathymodiolus azoricus, and a methanotrophic endosymbiont of Bathymodiolus puteoserpentis. The endosymbiont of R. pachyptila has a γ-CA gene in the genome. If α- and β-CA coding genes have been derived from other microorganisms, such as endosymbionts of T. jerichonana and Cycloclasticus sp. as the endosymbiont of B. heckerae, through HGT, the theory of the necessity of thermostable CA enzymes for survival in the extreme ecosystem of hydrothermal vents is suggested and helps the conservation of microbiome natural diversity in hydrothermal vents. These harsh ecosystems, with their integral players, such as HGT and endosymbionts, significantly impact the enrichment of life on Earth and the carbon cycle in the ocean.

Frankia alni Carbonic Anhydrase Regulates Cytoplasmic pH of Nitrogen-Fixing Vesicles

A phyloprofile of Frankia genomes was carried out to identify those genes present in symbiotic strains of clusters 1, 1c, 2 and 3 and absent in non-infective strains of cluster 4. At a threshold of 50% AA identity, 108 genes were retrieved. Among these were known symbiosis-associated genes such as nif (nitrogenase), and genes which are not know as symbiosis-associated genes such as can (carbonic anhydrase, CAN). The role of CAN, which supplies carbonate ions necessary for carboxylases and acidifies the cytoplasm, was thus analyzed by staining cells with pH-responsive dyes; assaying for CO₂ levels in N-fixing propionate-fed cells (that require a propionate-CoA carboxylase to yield succinate-CoA), fumarate-fed cells and N-replete propionate-fed cells; conducting proteomics on N-fixing fumarate and propionate-fed cells and direct measurement of organic acids in nodules and in roots. The interiors of both in vitro and nodular vesicles were found to be at a lower pH than that of hyphae. CO₂ levels in N₂-fixing propionate-fed cultures were lower than in N-replete ones. Proteomics of propionate-fed cells showed carbamoyl-phosphate synthase (CPS) as the most overabundant enzyme relative to fumarate-fed cells. CPS combines carbonate and ammonium in the first step of the citrulline pathway, something which would help manage acidity and NH₄⁺. Nodules were found to have sizeable amounts of pyruvate and acetate in addition to TCA intermediates. This points to CAN reducing the vesicles' pH to prevent the escape of NH₃ and to control ammonium assimilation by GS and GOGAT, two enzymes that work in different ways in vesicles and hyphae. Genes with related functions (carboxylases, biotin operon and citrulline-aspartate ligase) appear to have undergone decay in non-symbiotic lineages.

Carbonic Anhydrases: A Superfamily of Ubiquitous Enzymes

Numerous physiological and pathological cellular processes depend on the ability [...].

Structural Characterization of Thiadiazolesulfonamide Inhibitors Bound to Neisseria gonorrhoeae α-Carbonic Anhydrase

Drug-resistant Neisseria gonorrhoeae is a critical threat to public health, and bacterial carbonic anhydrases expressed by N. gonorrhoeae are potential new therapeutic targets to combat this pathogen. To further expand upon our recent reports of bacterial carbonic anhydrase inhibitors for the treatment of N. gonorrhoeae, our team has solved ligand-bound crystal structures of the FDA-approved carbonic anhydrase inhibitor acetazolamide, along with three analogs, in complex with the essential α-carbonic anhydrase isoform from N. gonorrhoeae. The structural data for the analogs presented bound to N. gonorrhoeae α-carbonic anhydrase supports the observed structure-activity relationship for in vitro inhibition with this scaffold against the enzyme. Moreover, the ligand-bound structures indicate differences in binding poses compared to those traditionally observed with the close human ortholog carbonic anhydrase II. These results present key differences in inhibitor binding between N. gonorrhoeae α-carbonic anhydrase and the human carbonic anhydrase II isoform.

Carbonic Anhydrase Inhibitors as Novel Antibacterials in the Era of Antibiotic Resistance: Where Are We Now?

Resistance to antibiotic treatment developed by bacteria in humans and animals occurs when the microorganisms resist treatment with clinically approved antibiotics. Actions must be implemented to stop the further development of antibiotic resistance and the subsequent emergence of superbugs. Medication repurposing/repositioning is one strategy that can help find new antibiotics, as it speeds up drug development phases. Among them, the Zn²⁺ ion binders, such as sulfonamides and their bioisosteres, are considered the most promising compounds to obtain novel antibacterials, thus avoiding antibiotic resistance. Sulfonamides and their bioisosteres have drug-like properties well-known for decades and are suitable lead compounds for developing new pharmacological agent families for inhibiting carbonic anhydrases (CAs). CAs are a superfamily of metalloenzymes catalyzing the reversible reaction of CO₂ hydration to HCO₃^- and H⁺, being present in most bacteria in multiple genetic families (α-, β-, γ- and ι-classes). These enzymes, acting as CO₂ transducers, are promising drug targets because their activity influences microbe proliferation, biosynthetic pathways, and pathogen persistence in the host. In their natural or slightly modified scaffolds, sulfonamides/sulfamates/sulamides inhibit CAs in vitro and in vivo, in mouse models infected with antibiotic-resistant strains, confirming thus their role in contrasting bacterial antibiotic resistance.

Comparative genomic insights into habitat adaptation of coral-associated Prosthecochloris

Green sulfur bacteria (GSB) are a distinct group of anoxygenic phototrophic bacteria that are found in many ecological niches. Prosthecochloris, a marine representative genus of GSB, was found to be dominant in some coral skeletons. However, how coral-associated Prosthecochloris (CAP) adapts to diurnal changing microenvironments in coral skeletons is still poorly understood. In this study, three Prosthecochloris genomes were obtained through enrichment culture from the skeleton of the stony coral Galaxea fascicularis. These divergent three genomes belonged to Prosthecochloris marina and two genomes were circular. Comparative genomic analysis showed that between the CAP and non-CAP clades, CAP genomes possess specialized metabolic capacities (CO oxidation, CO₂ hydration and sulfur oxidation), gas vesicles (vertical migration in coral skeletons), and cbb ₃-type cytochrome c oxidases (oxygen tolerance and gene regulation) to adapt to the microenvironments of coral skeletons. Within the CAP clade, variable polysaccharide synthesis gene clusters and phage defense systems may endow bacteria with differential cell surface structures and phage susceptibility, driving strain-level evolution. Furthermore, mobile genetic elements (MGEs) or evidence of horizontal gene transfer (HGT) were found in most of the genomic loci containing the above genes, suggesting that MGEs play an important role in the evolutionary diversification between CAP and non-CAP strains and within CAP clade strains. Our results provide insight into the adaptive strategy and population evolution of endolithic Prosthecochloris strains in coral skeletons.

The gram-negative bacterium Escherichia coli as a model for testing the effect of carbonic anhydrase inhibition on bacterial growth

Carbonic anhydrases, catalysing the reversible CO₂ hydration reaction, contribute in all living organisms to the maintenance of stable metabolic functions depending on intracellular concentrations of carbon dioxide, bicarbonate, and protons. Recent studies have examined how CAs affect bacterial lifecycle, considering these enzymes druggable targets due to interference with their activities by using inhibitors or activators. Here, we propose Escherichia coli cells as a model for testing the effect of acetazolamide (AZA), a potent CA inhibitor, on bacterial survival by evaluating E. coli growth through its glucose consumption. AZA, at concentrations higher than 31.2 µg/mL, was able to impair E. coli growth and glucose uptake. AZA is a good inhibitor of the two recombinant E. coli CAs, the β-CA CynT2, and the γ-CA EcoCAγ, with KIs of 227 and 248 nM, respectively. This study provides a proof-of-concept, low-cost method for identifying effective CA inhibitors capable of impairing bacterial metabolism.

A comparative study of carbonic anhydrase activity in lymphocytes from colorectal cancer tissues and adjacent healthy counterparts

Several carbonic anhydrase (CA, EC 4.2.1.1) isoforms play an essential role in processes connected to tumorigenesis, as they efficiently accelerate the hydration of carbon dioxide to bicarbonate and proton. In this context, examples are CA IX and CA XII, which were proved to be upregulated in many solid malignancies. On the other hand, cancer and the immune system are inextricably linked, and targeting the immune checkpoints recently was shown to efficiently improve the treatment of malignancies. In this study, we have investigated the expression of CA isoforms in tumour-infiltrating lymphocytes (TILs) that, according to the immunosurveillance theory, were suggested to have a crucial role in the development of colorectal cancer (CRC). T lymphocytes isolated from healthy surrounding mucosa showed a higher CA activity compared to those present in tumour and peripheral blood in the same patients. CA I and II were confirmed as enzyme isoforms involved in the process, as determined by proteomic analysis of corresponding TIL samples. These preliminary findings suggest a dysregulation of the local immune response in the CRC tissues and a loss of effective anticancer mechanisms mediated by CAs therein.

Carbonic Anhydrase Inhibitors from Marine Natural Products

Carbonic anhydrases (CAs, EC 4.2.1.1) are widespread metalloenzymes in organisms in all life kingdoms, being involved in pH regulation, metabolic processes and many other physiological and pathological conditions. CA inhibitors and activators thus possess applications as pharmacological agents in the management of a range of diseases. Marine natural products have allowed the identification of some highly interesting CA inhibitors, among which are sulfonamides, phenols, polyamines, coumarins and several other miscellaneous inhibitors, which are reviewed here. Psammaplin C and some bromophenols were the most investigated classes of such marine-based inhibitors and have been used as lead molecules for developing interesting types of potent and, in some cases, isoform-selective inhibitors, with applications as antitumor agents by inhibiting human CA XII and P-glycoprotein activities. Some phenols have shown interesting bacterial and fungal β-CA inhibitory effects. Marine natural products thus constitute a gold mine for identifying novel CA inhibitors, some of which may lead to the development of novel types of pharmacological agents.

May Sulfonamide Inhibitors of Carbonic Anhydrases from Mammaliicoccus sciuri Prevent Antimicrobial Resistance Due to Gene Transfer to Other Harmful Staphylococci?

Mammaliicoccus sciuri, previously known as Staphylococcus sciuri, is a Gram-positive bacterium involved in gene transfer phenomena that confer resistance to multiple antibiotics. These plasmid-encoded genes can be easily transferred to other pathogenic staphylococci. Because antibiotic resistance is rising, inhibiting M. sciuri proliferation may be a credible strategy for restricting antimicrobial resistance gene transfer to other pathogenic bacteria. Recently, it has been shown that blocking bacterial carbonic anhydrases (CAs, EC 4.2.1.1), metalloenzymes sustaining bacterial metabolic activities, can reduce pathogen survival and fitness. Here, the recombinant M. sciuri γ-CA (MscCAγ) has been cloned and purified, utilizing the DNA recombinant technology. Its kinetic properties for the CO₂ hydration reaction, as well as the sulfonamide inhibition profile, were investigated and compared with those reported earlier for MscCAβ (previously described as SauBCA) and the two off-target human CA isoforms (hCA I and hCA II). The recombinant MscCAγ showed significant hydratase activity. Moreover, the MscCAγ sulfonamide inhibitory profile was different from that of MscCAβ, implying that a varied amino acid set typifies the catalytic pocket of the two enzymes. These differences provide additional evidence for the possibility of developing novel CA class-specific inhibitors.

Thermophilic Water Gas Shift Reaction at High Carbon Monoxide and Hydrogen Partial Pressures in Parageobacillus thermoglucosidasius KP1013

The facultatively anaerobic Parageobacillus thermoglucosidasius oxidizes carbon monoxide to produce hydrogen via the water gas shift (WGS) reaction. In the current work, we examined the influence of carbon monoxide (CO) and hydrogen (H2) on the WGS reaction in the thermophilic P. thermoglucosidasius by cultivating two hydrogenogenic strains under varying CO and H2 compositions. Microbial growth and dynamics of the WGS reaction were monitored by evaluating parameters such as pressure, headspace composition, metabolic intermediates, pH, and optical density. Our analyses revealed that compared to the previously studied P. thermoglucosidasius strains, the strain KP1013 demonstrated higher CO tolerance and improved WGS reaction kinetics. Under anaerobic conditions, the lag phase before the WGS reaction shortened to 8 h, with KP1013 showing no hydrogen-induced product inhibition at hydrogen partial pressures up to 1.25 bar. The observed lack of product inhibition and the reduced lag phase of the WGS reaction support the possibility of establishing an industrial process for biohydrogen production with P. thermoglucosidasius.

Structure and Dynamics of the Isozymes II and IX of Human Carbonic Anhydrase

Human carbonic anhydrases (HCAs) are responsible for the pH control and sensing in our body and constitute key components in the central pH paradigm connected to cancer therapeutics. However, little or no molecular level studies are available on the pH-dependent stability and functional dynamics of the known isozymes of HCA. The main objective of this Article is to report the first bench-marking study on the structure and dynamics of the two most efficient isozymes, HCA II and IX, at neutral pH using classical molecular dynamics (MD) and constant pH MD (CpHMD) simulations combined with umbrella sampling, transition path sampling, and Markov state models. Starting from the known crystal structures of HCA II and the monomeric catalytic domain of HCA IX (labeled as HCA IX-c), we have generated classical MD and CpHMD trajectories (of length 1 μs each). In all cases, the overall stability, RMSD, and secondary structure segments of the two isozymes are found to be quite similar. Functionally important dynamics of these two enzymes have been probed in terms of active site hydration, coordination of the Zn(II) ion to a transient excess water, and the formation of putative proton transfer paths. The most important difference between the two isozymes is observed for the side-chain fluctuations of His-64 that is expected to shuttle an excess proton out of the active site as a part of the rate-determining intramolecular proton transfer reaction. The relative stability of the stable inward and outward conformations of the His-64 side-chain and the underlying free energy surfaces are found to depend strongly on the isozyme. In each case, a lower free energy barrier is detected between predominantly inward conformations from predominantly outward ones when simulated under constant pH conditions. The kinetic rate constants of interconversion between different free energy basins are found to span 10⁷-10⁸ s^-1 with faster conformational transitions predicted at constant pH condition. The estimated rate constants and free energies are expected to validate if the fluctuation of the His-64 side-chain in HCA IX may have a significance similar to that known in the multistep catalytic cycle of HCA II.

Design, Synthesis and Biological Evaluation of New Carbohydrate-Based Coumarin Derivatives as Selective Carbonic Anhydrase IX Inhibitors via “Click” Reaction

In this work, we designed a series of new carbohydrate-based coumarin carbonic anhydrase IX inhibitors by using 1,2,3-triazoles as linker. Next, these designed compounds were synthesized by the optimized one-pot click chemistry reaction condition. Subsequently, these target compounds were assayed for the inhibition of three carbonic anhydrase isoforms (CA I, CA II and CA IX). Intriguingly, all the compounds showed better CA IX inhibitory activity than initial coumarin fragments. Among them, compound 10a (IC₅₀: 11 nM) possessed the most potent CA IX inhibitory activity, which was more potent than the reference drug acetazolamide (IC₅₀: 30 nM). Notably, compound 10a showed 3018-fold, 1955-fold selectivity relative to CA I and CA II, respectively. Meanwhile, representative compounds could reduce tumor cell viability and the extracellular acidification in HT-29 and MDA-MB-231 cancer cell lines. Even more interestingly, our target compounds had no apparent cytotoxicity toward MCF-10A cell line. In addition, the in vitro stability assays also indicated our developed compounds possessed good liver microsomal metabolic stabilities and plasma stability. Furthermore, representative compounds revealed relatively low hERG cardiac toxicity and acute toxicity. Furthermore, docking studies were carried out to understand the interactions of our target compounds with the protein target CA IX. Collectively, our results suggest that compound 10a, as a selective CA IX inhibitor, could be an important lead compound for further optimization and development as an anticancer agent.