Cloning, expression and purification of the α-carbonic anhydrase from the mantle of the Mediterranean mussel, Mytilus galloprovincialis

We cloned, expressed, purified, and determined the kinetic constants of the recombinant α-carbonic anhydrase (rec-MgaCA) identified in the mantle tissue of the bivalve Mediterranean mussel, Mytilus galloprovincialis. In metazoans, the α-CA family is largely represented and plays a pivotal role in the deposition of calcium carbonate biominerals. Our results demonstrated that rec-MgaCA was a monomer with an apparent molecular weight of about 32 kDa. Moreover, the determined kinetic parameters for the CO₂ hydration reaction were k_cat =  4.2 × 10⁵ s⁻¹ and k_cat/K_m of 3.5 × 10⁷ M⁻¹ ×s⁻¹. Curiously, the rec-MgaCA showed a very similar kinetic and acetazolamide inhibition features when compared to those of the native enzyme (MgaCA), which has a molecular weight of 50 kDa. Analysing the SDS-PAGE, the protonography, and the kinetic analysis performed on the native and recombinant enzyme, we hypothesised that probably the native MgaCA is a multidomain protein with a single CA domain at the N-terminus of the protein. This hypothesis is corroborated by the existence in mollusks of multidomain proteins with a hydratase activity. Among these proteins, nacrein is an example of α-CA multidomain proteins characterised by a single CA domain at the N-terminus part of the entire protein.

Exploring Heteroaryl-pyrazole Carboxylic Acids as Human Carbonic Anhydrase XII Inhibitors

We report the synthesis, biological evaluation, and structural study of a series of substituted heteroaryl-pyrazole carboxylic acid derivatives. These compounds have been developed as inhibitors of specific isoforms of carbonic anhydrase (CA), with potential as prototypes of a new class of chemotherapeutics. Both X-ray crystallography and computational modeling provide insights into the CA inhibition mechanism. Results indicate that this chemotype produces an indirect interference with the zinc ion, thus behaving differently from other related nonclassical inhibitors. Among the tested compounds, 2c with K_i = 0.21 μM toward hCA XII demonstrated significant antiproliferative activity against hypoxic tumor cell lines. Taken together, the results thus provide the basis of structural determinants for the development of novel anticancer agents.

Production and covalent immobilisation of the recombinant bacterial carbonic anhydrase (SspCA) onto magnetic nanoparticles

Carbonic anhydrases (CAs; EC 4.2.1.1) are metalloenzymes with a pivotal potential role in the biomimetic CO₂ capture process (CCP) because these biocatalysts catalyse the simple but physiologically crucial reaction of carbon dioxide hydration to bicarbonate and protons in all life kingdoms. The CAs are among the fastest known enzymes, with k_cat values of up to 10⁶ s^-1 for some members of the superfamily, providing thus advantages when compared with other CCP methods, as they are specific for CO₂. Thermostable CAs might be used in CCP technology because of their ability to perform catalysis in operatively hard conditions, typical of the industrial processes. Moreover, the improvement of the enzyme stability and its reuse are important for lowering the costs. These aspects can be overcome by immobilising the enzyme on a specific support. We report in this article that the recombinant thermostable SspCA (α-CA) from the thermophilic bacterium Sulfurihydrogenibium yellowstonense can been heterologously produced by a high-density fermentation of Escherichia coli cultures, and covalently immobilised onto the surface of magnetic Fe₃O₄ nanoparticles (MNP) via carbodiimide activation reactions. Our results demonstrate that using a benchtop bioprocess station and strategies for optimising the bacterial growth, it is possible to produce at low cost a large amount SspCA. Furthermore, the enzyme stability and storage greatly increased through the immobilisation, as SspCA bound to MNP could be recovered from the reaction mixture by simply using a magnet or an electromagnetic field, due to the strong ferromagnetic properties of Fe₃O₄.

N-Substituted and ring opened saccharin derivatives selectively inhibit transmembrane, tumor-associated carbonic anhydrases IX and XII

A series of N-substituted saccharins incorporating aryl, alkyl and alkynyl moieties, as well as some ring opened derivatives were prepared and investigated as inhibitors of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1). The widespread cytosolic isoforms CA I and II were not inhibited by these sulfonamides whereas transmembrane, tumor-associated ones were effectively inhibited, with K_Is in the range of 22.1-481nM for CA IX and of 3.9-245nM for hCA XII. Although the inhibition mechanism of these tertiary/secondary sulfonamides is unknown for the moment, the good efficacy and especially selectivity for the inhibition of the tumor-associated over the cytosolic, widespread isoforms, make these derivatives of considerable interest as enzyme inhibitors with various pharmacologic applications.

Carbonic anhydrase activation enhances object recognition memory in mice through phosphorylation of the extracellular signal-regulated kinase in the cortex and the hippocampus

Rats injected with by d-phenylalanine, a carbonic anhydrase (CA) activator, enhanced spatial learning, whereas rats given acetazolamide, a CA inhibitor, exhibited impairments of fear memory consolidation. However, the related mechanisms are unclear. We investigated if CAs are involved in a non-spatial recognition memory task assessed using the object recognition test (ORT). Systemic administration of acetazolamide to male CD1 mice caused amnesia in the ORT and reduced CA activity in brain homogenates, while treatment with d-phenylalanine enhanced memory and increased CA activity. We provided also the first evidence that d-phenylalanine administration rapidly activated extracellular signal-regulated kinase (ERK) pathways, a critical step for memory formation, in the cortex and the hippocampus, two brain areas involved in memory processing. Effects elicited by d-phenylalanine were completely blunted by co-administration of acetazolamide, but not of 1-N-(4-sulfamoylphenyl-ethyl)-2,4,6-trimethylpyridinium perchlorate ^(C18), a CA inhibitor that, differently from acetazolamide, does not cross the blood brain barrier. Our results strongly suggest that brain but not peripheral CAs activation potentiates memory as a result of ERK pathway enhanced activation.

Comparison of the Sulfonamide Inhibition Profiles of the β- and γ-Carbonic Anhydrases from the Pathogenic Bacterium Burkholderia pseudomallei

We have cloned, purified, and characterized a β-carbonic anhydrase (CA, EC 4.2.1.1), BpsCAβ, from the pathogenic bacterium Burkholderia pseudomallei, responsible for the tropical disease melioidosis. The enzyme showed high catalytic activity for the physiologic CO₂ hydration reaction to bicarbonate and protons, with the following kinetic parameters: kcat of 1.6 × 10⁵ s-1 and kcat/KM of 3.4 × 10⁷ M-1 s-1. An inhibition study with a panel of 38 sulfonamides and one sulfamate-including 15 compounds that are used clinically-revealed an interesting structure-activity relationship for the interaction of this enzyme with these inhibitors. Many simple sulfonamides and clinically used agents such as topiramate, sulpiride, celecoxib, valdecoxib, and sulthiame were ineffective BpsCAβ inhibitors (KI > 50 µM). Other drugs, such as ethoxzolamide, dorzolamide, brinzolamide, zonisamide, indisulam, and hydrochlorothiazide were moderately potent micromolar inhibitors. The best inhibition was observed with benzene-1,3-disulfonamides-benzolamide and its analogs acetazolamide and methazolamide-which showed KI in the range of 185-745 nM. The inhibition profile of BpsCAβ is very different from that of the γ-class enzyme from the same pathogen, BpsCAγ. Thus, identifying compounds that would effectively interact with both enzymes is relatively challenging. However, benzolamide was one of the best inhibitors of both of these CAs with KI of 653 and 185 nM, respectively, making it an interesting lead compound for the design of more effective agents, which may be useful tools for understanding the pathogenicity of this bacterium.

Comparison of the anion inhibition profiles of the β- and γ-carbonic anhydrases from the pathogenic bacterium Burkholderia pseudomallei

We report the cloning, purification and characterization of BpsβCA, a β-class carbonic anhydrase (CA, EC 4.2.1.1) from the pathogenic bacterium Burkholderia pseudomallei, the etiological agent of melioidosis, and compare its activity and inhibition with those of the γ-CA from the same organism, BpsγCA, recently investigated by our groups. BpsβCA showed a significant catalytic activity for the physiologic, CO₂ hydration reaction, with the following kinetic parameters, k_cat of 1.6×10⁵s^-1 and k_cat/K_m of 3.4×10⁷M^-1×s^-1. The inhibition of BpsβCA with a group of anions and small molecules was also investigated. The best inhibitors were sulfamide, sulfamic acid and phenylarsonic acid, which showed K_Is in the range of 83-92µM, whereas phenylboronic acid, fluoride, cyanide, azide, bisulfite, tetraborate, perrhenate, perruthenate, peroxydisulfate, perchlorate, tetrafluoroborate, fluorosulfonate and hexafluorophosphate showed K_Is>100mM. Other inhibitors of this new enzyme were bicarbonate, trithiocarbonate, some complex inorganic anions and N,N-diethyldithiocarbamate, which had inhibition constants of 0.32-8.6mM. As little is known of the life cycle and virulence of this bacterium, this type of study may bring information of interest for the development of novel strategies to fight bacterial infection and drug resistance to commonly used antibiotics.

Design and Synthesis of Novel Nonsteroidal Anti-Inflammatory Drugs and Carbonic Anhydrase Inhibitors Hybrids (NSAIDs-CAIs) for the Treatment of Rheumatoid Arthritis

We report the synthesis of a series of hybrid compounds incorporating 6- and 7-substituted coumarins (carbonic anhydrase, CA inhibitors) derivatized with clinically used NSAIDs (indomethacin, sulindac, ketoprofen, ibuprofen, diclofenac, ketorolac, etc., cyclooxygenase inhibitors) as agents for the management of rheumatoid arthritis (RA). Most compounds were effective in inhibiting the RA overexpressed hCA IX and XII, with K_I values in the low nanomolar-subnanomolar ranges. The antihyperalgesic activity of such compounds was assessed by means of the paw-pressure and incapacitance tests using an in vivo RA model. Among all tested compounds, the 7-coumarine hybrid with ibuprofen showed potent and persistent antihyperalgesic effect up to 60 min after administration.

Anion inhibition profiles of the γ-carbonic anhydrase from the pathogenic bacterium Burkholderia pseudomallei responsible of melioidosis and highly drug resistant to common antibiotics

Burkholderia pseudomallei is a Gram-negative saprophytic bacterium responsible of melioidosis, an endemic disease of tropical and sub-tropical regions of the world. A recombinant γ-CA (BpsγCA) identified in the genome of this bacterium was cloned and purified. Its catalytic activity and anion inhibition profiles were investigated. The enzyme was an efficient catalyst for the CO₂ hydration showing a k_cat of 5.3×10⁵s^-1 and k_cat/K_m of 2.5×10⁷M^-1×s^-1. The best BpsγCA inhibitors were sulfamide, sulfamic acid, phenylboronic acid and phenylarsonic acid, which showed K_I in the range of 49-83μM (these inhibitors showed millimolar inhibition constant against hCA II), followed by diethyldithiocarbamate, selenate, tellurate, perrhenate, selenocyanate, trithiocarbonate, tetraborato, pyrophosphate, stannate, carbonate, bicarbonate, azide, cyanide, thiocyanate and cyanate with K_Is in the range of 0.55-9.1mM. In our laboratories, work is in progress to resolve the X-ray crystal structures of BpsγCA, which may allow the development of small molecule inhibitors with desired properties for targeting and inhibiting specifically the bacterial over the human CAs, considering the fact that B. pseudomallei is involved in a serious bacterial disease.

Burkholderia pseudomallei γ-carbonic anhydrase is strongly activated by amino acids and amines

Activation of the γ-class carbonic anhydrase (CAs, EC 4.2.1.1) from the pathogenic bacterium Burkholderia pseudomallei (BpsγCA) with a series of natural and non-natural amino acids and aromatic/heterocyclic amines has been investigated. The best BpsγCA activators were d-His, l-DOPA, d-Trp, 4-amino-l-Phe, dopamine, 2-(2-aminoethyl)pyridine, 2-aminoethyl-piparazine/morpholine and l-adrenaline, which showed activation constants ranging between 9 and 86nM. The least effective activators were l-His, l-Phe and 2-pyridyl-methylamine, with K_As in the range of 1.73-24.7μM. As little is known about the role of γ-CAs in the lifecycle and virulence of this saprophytic bacterium, this study may shed some light on such phenomena. This is the first CA activation study of a γ-CA from a pathogenic bacterium, the only other such study being on the enzyme discovered in the archaeon Methanosarcina thermophila, Cam.

Anion inhibition profiles of the complete domain of the η-carbonic anhydrase from Plasmodium falciparum

We have cloned, purified and investigated the catalytic activity and anion inhibition profiles of a full catalytic domain (358 amino acid residues) carbonic anhydrase (CA, EC 4.2.1.1) from Plasmodium falciparum, PfCAdom, an enzyme belonging to the η-CA class and identified in the genome of the malaria-producing protozoa. A truncated such enzyme, PfCA1, containing 235 residues was investigated earlier for its catalytic and inhibition profiles. The two enzymes were efficient catalysts for CO2 hydration: PfCAdom showed a kcat of 3.8×10(5)s(-1) and kcat/Km of 7.2×10(7)M(-1)×s(-1), whereas PfCA showed a lower activity compared to PfCAdom, with a kcat of 1.4×10(5)s(-1) and kcat/Km of 5.4×10(6)M(-1)×s(-1). PfCAdom was generally less inhibited by most anions and small molecules compared to PfCA1. The best PfCAdom inhibitors were sulfamide, sulfamic acid, phenylboronic acid and phenylarsonic acid, which showed KIs in the range of 9-68μM, followed by bicarbonate, hydrogensulfide, stannate and N,N-diethyldithiocarbamate, which were submillimolar inhibitors, with KIs in the range of 0.53-0.97mM. Malaria parasites CA inhibition was proposed as a new strategy to develop antimalarial drugs, with a novel mechanism of action.

Active Components of Essential Oils as Anti-Obesity Potential Drugs Investigated by in Silico Techniques

In this study, for the first time, we have considered essential oils (EOs) as possible resources of carbonic anhydrase inhibitors (CAIs), in particular against the mitochondrial isoform VA that, actually, represents an innovative target for the obesity treatment. In silico structure-based virtual screening was performed in order to speed up the identification of promising antiobesity agents. The potential hit compounds were submitted to in vitro assays and experimental results, corroborated by molecular modeling studies, showed EOs components as a new class of CAIs with a competitive mechanism of action due to the zinc ion coordination within the active sites of these metallo-enzymes.

Indazole, Pyrazole, and Oxazole Derivatives Targeting Nitric Oxide Synthases and Carbonic Anhydrases

Nitric oxide (NO) is an essential endogenous mediator with a physiological role in the central nervous system as neurotransmitter and neuromodulator. A growing number of studies have demonstrated that abnormal nitrergic signaling is a crucial event in the development of neurodegeneration. In particular, the uncontrolled production of NO by neuronal nitric oxide synthase (nNOS) is observed in several neurodegenerative diseases. Moreover, it is well recognized that specific isoforms of human carbonic anhydrase (hCA) physiologically modulate crucial pathways of signal processing and that low expression of CA affects cognition, leading to mental retardation, Alzheimer's disease, and aging-related cognitive impairments. In light of this, dual agents that are able to target both NOS (inhibition) and CA (activation) could be useful drug candidates for the treatment of Alzheimer's disease, aging, and other neurodegenerative diseases. In the present work, we show the design, synthesis, and in vitro biological evaluation of new nitrogen-based heterocyclic compounds. Among the tested molecules, 2-amino-3-(4-hydroxyphenyl)-N-(1H-indazol-5-yl)propanamide hydrochloride (10 b) was revealed to be a potent dual agent, able to act as a selective nNOS inhibitor and activator of the hCA I isoform.

Discovery of New Potential Anti-Infective Compounds Based on Carbonic Anhydrase Inhibitors by Rational Target-Focused Repurposing Approaches

In academia, compound recycling represents an alternative drug discovery strategy to identify new pharmaceutical targets from a library of chemical compounds available in house. Herein we report the application of a rational target-based drug-repurposing approach to find diverse applications for our in-house collection of compounds. The carbonic anhydrase (CA, EC 4.2.1.1) metalloenzyme superfamily was identified as a potential target of our compounds. The combination of a thoroughly validated docking screening protocol, together with in vitro assays against various CA families and isoforms, allowed us to identify two unprecedented chemotypes as CA inhibitors. The identified compounds have the capacity to preferentially bind pathogenic (bacterial/protozoan) CAs over human isoforms and represent excellent hits for further optimization in hit-to-lead campaigns.

Monothiocarbamates Strongly Inhibit Carbonic Anhydrases in Vitro and Possess Intraocular Pressure Lowering Activity in an Animal Model of Glaucoma

A series of monothiocarbamates (MTCs) were prepared from primary/secondary amines and COS as potential carbonic anhydrase (CA, EC 4.2.1.1) inhibitors, using the dithiocarbamates, the xanthates, and the trithiocarbonates as lead compounds. The MTCs effectively inhibited the pharmacologically relevant human (h) hCAs isoforms I, II, IX, and XII in vitro and showed KIs spanning between the low and medium nanomolar range. By means of a computational study, the MTC moiety binding mode on the CAs was explained. Furthermore, a selection of MTCs were evaluated in a normotensive glaucoma rabbit model for their intraocular pressure (IOP) lowering effects and showed interesting activity.

A substituted sulfonamide and its Co (II), Cu (II), and Zn (II) complexes as potential antifungal agents

A sulfonamide 1-tosyl-1-H-benzo(d)imidazol-2-amine (TBZA) and three new complexes of Co(II), Cu(II), and Zn(II) have been synthesized. The compounds have been characterized by elemental analyses, FTIR, ¹H, and ¹³C-NMR spectroscopy. The structure of the TBZA, and its Co(II) and Cu(II) complexes, was determined by X-ray diffraction methods. TBZA and its Co(II) complex crystallize in the triclinic P-1 space group, while the Cu(II) complex crystallizes in the monoclinic P2₁/c space group. Antifungal activity was screened against eight pathogenic yeasts: Candida albicans (DMic 972576), Candida krusei (DMic 951705), Candida glabrata (DMic 982882), Candida tropicalis (DMic 982884), Candida dubliniensis (DMic 93695), Candida guilliermondii (DMic 021150), Cryptococcus neoformans (ATCC 24067), and Cryptococcus gattii (ATCC MYA-4561). Results on the inhibition of various human (h) CAs, hCA I, II, IV, VII, IX, and XII, and pathogenic beta and gamma CAs are also reported.