Human Cytosolic Carbonic Anhydrase Research Articles

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 (KIs of 31.5–637.3 nM) and excellent hCA II (KIs in the range of 1.3–13.7 nM) and hCA VII inhibitors (KIs 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 KI of 73.6 nM, considerably better than AAZ (KI of 625 nM). The tested compounds displayed medium inhibitory potency against StCA1 (KIs of 69.2–163.3 nM) when compared to the standard drug (KI of 59 nM). However, StCA2 was poorly inhibited by the sulphonamides reported here, with KIs in the micromolar range between 275.2 and 4875.0 nM.

The synthesis, biological evaluation and in silico studies of asymmetric 3,5-diaryl-rhodanines as novel inhibitors of human carbonic anhydrase isoenzymes

The synthesis of rhodanine core, which forms the main skeleton of organics used as a large number of drugs, is obtained with more green approaches is very significant. Additionally, asymmetrical functionalization from C5 and N(3) positions of 3-NH2-Rh (1) via a green approach is representing a challenge. In this connect, the primary goal of this study is to obtain novel asymmetric 3,5-diarylRhs by an effective green synthetic approach. For this, initially, the reactions of the variety of aromatic aldehydes with 5-Ar-Rhs 2a and 2b were investigated by changing parameters such as catalyst, solvent, and temperature. As a result of the studies, novel asymmetric 3,5-diarylRhs were obtained as the main product of acetic acid catalyst reactions carried out at reflux temperatures of ethanol. Moreover, the site-selective reduction of the imine group in the structure of the asymmetric 3,5-diarylRhs was also carried out within the scope of this study. Following synthesis, we also carried out inhibition studies of novel 3,5-diarylRhs against cytosolic human carbonic anhydrase I, and II (hCA I and II) isoforms. As a result of these inhibition studies, inhibition constants (Ki) for hCA I and hCA II were found in the range of 107.26 ± 31.18 to 601.97 ± 46.44 nM, and 127.72 ± 15.75 to 480.13 ± 47.24 nM, respectively. In order to support the results obtained as a result of the inhibition studies, molecular docking studies of the asymmetrical 3,5-diarylRhs 4i and 4l showing the best activity for hCA I and hCA II were also carried out, and the morphology of the binding was examined. Furthermore, the organics comply with Lipinski's and Jorgensen's rules of all compounds were determined by calculated ADME and drug-likeness parameters. That is, the ADME and drug-likeness parameters of the new 3,5-diarylRhs showed that they are not only with hCA I and hCA II inhibitory activities but also with appropriate drug-likeness properties and physicochemical parameters.

Carbonic anhydrases enhance activity of endogenous Na-H exchangers and not the electrogenic Na/HCO3 cotransporter NBCe1-A, expressed in Xenopus oocytes.

According to the metabolon hypothesis, direct association of cytosolic carbonic anhydrases (CAs) with the electrogenic Na/HCO3 cotransporter NBCe1-A speeds transport by regenerating/consuming . The present work addresses published discrepancies as to whether cytosolic CAs stimulate NBCe1-A, heterologously expressed in Xenopus oocytes. We confirm the essential elements of the previous experimental observations, taken as support for the metabolon hypothesis. However, using our own experimental protocols or those of others, we find that NBCe1-A function is unaffected by cytosolic CAs. Previous conclusions that cytosolic CAs do stimulate NBCe1-A can be explained by an unanticipated stimulatory effect of the CAs on an endogenous Na-H exchanger. Theoretical analyses show that, although CAs could stimulate non- transporters (e.g. Na-H exchangers) by accelerating CO2 / -mediated buffering of acid-base equivalents, they could not appreciably affect transport rates of NBCe1 or other transporters carrying , , or ion pairs. The metabolon hypothesis predicts that cytosolic carbonic anhydrase (CA) binds to NBCe1-A, promotes replenishment/consumption, and enhances transport. Using a short step-duration current-voltage (I-V) protocol with Xenopus oocytes expressing eGFP-tagged NBCe1-A, our group reported that neither injecting human CA II (hCA II) nor fusing hCA II to the NBCe1-A carboxy terminus affects background-subtracted NBCe1 slope conductance (GNBC ), which is a direct measure of NBCe1-A activity. Others - using bovine CA (bCA), untagged NBCe1-A, and protocols keeping holding potential (Vh ) far from NBCe1-A's reversal potential (Erev ) for prolonged periods - found that bCA increases total membrane current (ΔIm ), which apparently supports the metabolon hypothesis. We systematically investigated differences in the two protocols. In oocytes expressing untagged NBCe1-A, injected with bCA and clamped to -40mV, CO2 / exposures markedly decrease Erev , producing large transient outward currents persisting for >10min and rapid increases in [Na+ ]i . Although the CA inhibitor ethoxzolamide (EZA) reduces both ΔIm and d[Na+ ]i /dt, it does not reduce GNBC . In oocytes not expressing NBCe1-A, CO2 / triggers rapid increases in [Na+ ]i that both hCA II and bCA enhance in concentration-dependent manners. These d[Na+ ]i /dt increases are inhibited by EZA and blocked by EIPA, a Na-H exchanger (NHE) inhibitor. In oocytes expressing untagged NBCe1-A and injected with bCA, EIPA abolishes the EZA-dependent decreases in ΔIm and d[Na+ ]i /dt. Thus, CAs/EZA produce their ΔIm and d[Na+ ]i /dt effects not through NBCe1-A, but endogenous NHEs. Theoretical considerations argue against a CA stimulation of transport, supporting the conclusion that an NBCe1-A- metabolon does not exist in oocytes.

Synthesis and characterization of some new pyrazolines and their inhibitory potencies against carbonic anhydrases.

The inhibition of the two human cytosolic carbonic anhydrase (hCA; EC 4.2.1.1) isozymes I and II with some new pyrazoline derivatives was investigated for the first time. The structures of the newly synthesized pyrazoline derivatives were characterized by Fourier transform-infrared spectroscopy, 1 H-/13 C-nuclear magnetic resonance, and mass spectrometry, and elemental analysis. Compounds 1-6 showed Ki values in the range of 16.4-205.9 nM for hCA I and of 6.08-93.21 nM against hCA II. These hydroxyl and amino group-containing compounds generally were competitive inhibitors. The compounds investigated here showed effective hCA I and II inhibitory effects, in the same range as the clinically used acetazolamide, and might be used as leads for generating enzyme inhibitors, possibly targeting other CA isoforms that have not yet been assayed for their interactions with such agents.

Pyrrolo and pyrrolopyrimidine sulfonamides act as cytotoxic agents in hypoxia via inhibition of transmembrane carbonic anhydrases

A series of novel sulfonamide derivatives bearing pyrrole and pyrrolopyrimidine scaffolds were synthesized and screened as carbonic anhydrase inhibitors. The inhibition activity of the synthesized compounds was evaluated against the cytosolic human carbonic anhydrase isoforms I and II and the transmembranal isoforms IX and XII. Several candidates showed potent inhibitory activity against IX and XII isoforms. Furthermore, ex vivo screening of cytotoxic selectivity and activity of the most potent derivatives were carried out against normal cells (WI38) and cervical cancer cell line (HeLa) under normal and hypoxic conditions using acetazolamide as reference drug. Compound 11b potency was nearly three folds higher in hypoxic than normoxic condition whereas that of compound 11f was nearly four folds higher in hypoxic vs. normoxic HeLa cells. All the screened derivatives exhibited less potency on normal cells (WI38). Molecular docking was carried out to discover the possible binding mode of compounds within the active site of isoform CA IX.

Intermolecular amination of allylic and benzylic alcohols leads to effective inhibitions of acetylcholinesterase enzyme and carbonic anhydrase I and II isoenzymes.

In this study, we aimed to determine the inhibition effects of novel synthesized sulfamates (2a-g), sulfonamides (3b-f), carbonyl sulfonamides (3h and i), and carbonyl sulfamates (4h and 4i), which were tested against two human cytosolic carbonic anhydrase I and II isozymes (hCA I and II) and acetylcholinesterase (AChE) enzyme. For inhibition properties of allylic sulfamates, the half maximal inhibitory concentration (IC50 ) and inhibition constant (Ki ) were calculated for each novel compounds. The allylic sulfamates showed that Ki values are in the range of 187.33-510.31 pM for hCA I, 104.22-290.09 pM against hCA II, and 12.73-103.63 pM against AChE. The results demonstrated that all newly synthesized compounds had shown effective inhibition against hCA I and II isoenzymes and AChE enzyme.

Steered Molecular Dynamics Simulations of Coumarin2 5Z/5E Pulling Reveal Different Interaction Profiles for Four Human Cytosolic Carbonic Anhydrases

Carbonic anhydrase (CA) is an important enzyme, which has multiple isoforms each performing different functions in humans. Characterizing the interactions of carbonic anhydrase isoforms with ligands is a difficult but important task. In recent years, steered molecular dynamics (SMD) has been used successfully to characterize ligand binding and unbinding events. In this study, constant velocity SMD simulations were performed on four cytosolic human carbonic anhydrases (carbonic anhydrase I, II, III and VII) using a ligand called Coumarin2 5Z/5E to understand better the nature of interactions between this ligand and the various enzyme isoforms. The influence of force constant and pulling velocity on SMD simulations were investigated. When the force constant and the pulling velocity were changed, no significant effect on interaction profiles was observed. Finally, hydrogen bond interactions, Histidine 64 positions and the differences between force-distance profiles for all isozymes were analyzed. These results demonstrate that human cytosolic carbonic anhydrases I, III, and VII show similar Coumarin2 5Z/5E unbinding patterns with different rupture forces, while carbonic anhydrase II has a distinct interaction profile.

Synthesis of novel benzenesulfamide derivatives with inhibitory activity against human cytosolic carbonic anhydrase I and II and Vibrio cholerae α- and β-class enzymes

The synthesis of a new series of sulfamides incorporating ortho-, meta, and para-benzenesulfamide moieties is reported, which were investigated for the inhibition of two human (h) isoforms of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1), hCA I and II, and two Vibrio cholerae enzymes, belonging to the α- and β-CA classes (VchCAα, VchCAβ). The compounds were prepared by using the “tail approach”, aiming to overcome the scarcity of selective inhibition profiles associated to CA inhibitors belonging to the zinc binders. The built structure–activity relationship showed that the incorporation of benzhydryl piperazine tails on a phenyl sulfamide scaffold determines rather good efficacies against hCA I and VchCAα, with several compounds showing KIs < 100 nM. The activity was lower against hCA II and VchCAβ, probably due to the fact that the incorporated tails are quite bulky. The obtained evidences allow us to continue the investigations of different tails/zinc binding groups, with the purpose to increase the effectiveness/selectivity of such inhibitors against bacterial CAs from pathogens, affording thus potential new anti-infectives.

The synthesis of axially disubstituted silicon phthalocyanines, their quaternized derivatives and first inhibitory effect on human cytosolic carbonic anhydrase isozymes hCA I and II.

In this study a novel silicon(iv) phthalocyanine bearing [(2E)-3-[4-(dimethylamino)phenyl]-1-(4-phenoxy)prop-2-en-1-one] group and its quaternized derivative at their axial positions were synthesized for the first time. Axially disubstituted silicon(iv) phthalocyanines were also characterized by various spectroscopic techniques. The inhibition of two human cytosolic carbonic anhydrase (hCA, EC 4.2.1.1) isozymes I and II, with axially disubstituted silicon phthalocyanines and their quaternized derivatives were investigated by using the esterase assay, with 4-nitrophenyl acetate as substrate. Silicon phthalocyanines ZM-1-Si, ZM-5-Si, ZT-Si and their quaternized derivatives ZM-1-SiQ, ZM-5-SiQ, ZT-SiQ showed IC50 values in the range of 0.0178–0.1653 μM for hCA I and of 0.0172–0.1212 μM against hCA II, respectively. This study is the first example of carbonic anhydrase enzyme inhibition of phthalocyanines.

1,3-Oxazole-based selective picomolar inhibitors of cytosolic human carbonic anhydrase II alleviate ocular hypertension in rabbits: Potency is supported by X-ray crystallography of two leads

Two lead 1,3-oxazole-based carbonic anhydrase inhibitors (CAIs) earlier identified as selective, picomolar inhibitors of hCA II (a cytosolic target for treatment of glaucoma) have been investigated further. Firstly, they were found to be conveniently synthesized on multigram scale, which enables further development. These compounds were found to be comparable in efficacy to dorzolamide eye drops when applied in the eye drop form as well. Finally, the reasons for unusually high potency of these compounds became understood from their high-resolution X-ray crystallography structures. These data significantly expand our understanding of heterocycle-based primary sulfonamides, many of which have recently emerged from our labs - particularly, from the corneal permeability standpoint.

Novel NHC Precursors: Synthesis, Characterization, and Carbonic Anhydrase and Acetylcholinesterase Inhibitory Properties.

Three series of imidazolidinium ligands (NHC precursors) substituted with 4-vinylbenzyl, 2-methyl-1,4-benzodioxane, and N-propylphthalimide were synthesized. N-Heterocyclic carbene (NHC) precursors were prepared from N-alkylimidazoline and alkyl halides. The novel NHC precursors were characterized by 1 H NMR, 13 C NMR, FTIR spectroscopy, and elemental analysis techniques. The enzymes inhibition activities of the NHC precursors were investigated against the cytosolic human carbonic anhydrase I and II isoenzymes (hCA I and II) and the acetylcholinesterase (AChE) enzyme. The inhibition parameters (IC50 and Ki values) were calculated by spectrophotometric method. The inhibition constants (Ki ) were found to be in the range of 166.65-635.38 nM for hCA I, 78.79-246.17 nM for hCA II, and 23.42-62.04 nM for AChE. Also, the inhibitory effects of the novel synthesized NHCs were compared to acetazolamide as a clinical CA isoenzymes inhibitor and tacrine as a clinical cholinergic enzymes inhibitor.

A novel proton transfer salt of 2-amino-6-sulfamoylbenzothiazole and its metal complexes: the evaluation of their inhibition effects on human cytosolic carbonic anhydrases

A novel proton transfer compound (SMHABT)+(HDPC)− (1) obtained from 2-amino-6-sulfamoylbenzothiazole (SMABT) and 2,6-pyridinedicarboxylic acid (H2DPC) and its Fe(III), Co(II), Ni(II) complexes (2–4), and Fe(II) complex of SMABT (5) have been prepared and characterized by spectroscopic techniques. Additionally, single crystal X-ray diffraction techniques were applied to complexes (2–4). All complexes (2–4) have distorted octahedral conformations and the structure of 5 might be proposed as octahedral according to spectral and analytical results. All compounds, including acetazolamide (AAZ) as the control compound, were also evaluated for their in vitro inhibition effects on human hCA I and hCA II for their hydratase and esterase activities. The synthesized compounds have remarkable inhibitory activities on hCA I and hCA II. Especially, the inhibition potentials of the salt and the metal complexes (1–5) are comparable with AAZ. Inhibition data have been analyzed by using a one-way analysis of variance for multiple comparisons (p < .0001).

The synthesis of novel pyrazole-3,4-dicarboxamides bearing 5-amino-1,3,4-thiadiazole-2-sulfonamide moiety with effective inhibitory activity against the isoforms of human cytosolic carbonic anhydrase I and II

A series of 1-(3-substituted-phenyl)-5-phenyl-N3,N4-bis(5-sulfamoyl-1,3,4-thiadiazol-2-yl)-1H-pyrazole-3,4-dicarboxamides (4–15) were synthesized. The structures of these pyrazole-sulfonamides were confirmed by FT-IR, 1H NMR, 13C NMR and elemental analysis methods. Human cytosolic carbonic anhydrase (CA, EC 4.2.1.1) isozymes (hCA I and II) were purified from erythrocyte cells by affinity chromatography. The inhibitory effects of newly synthesized derivatives (4–15) were investigated in vitro on esterase activities of these isozymes. The Ki values were determined as 0.119–3.999μM for hCA I and 0.084–0.878μM for hCA II. The results showed that the compound 6 for hCA I and the compound 11 for hCA II had the highest inhibitory effect. Beside that, the compound 8 had the lowest inhibition effect on both isozymes.

Pyridazinone substituted benzenesulfonamides as potent carbonic anhydrase inhibitors.

A series of sulfonamide derivatives (2a-l) incorporating substituted pyridazinone moieties were investigated for the inhibition of two human cytosolic carbonic anhydrase isoforms, hCA I and hCA II. All these compounds, together with the clinically used sulfonamide acetazolamide were investigated as inhibitors of the physiologically relevant isozymes I and II. These sulfonamides showed very strong inhibition against all these isoforms with K(I)'s in the range of 0.98-8.5 nM which makes such molecules possible to be used as leads for discovery of novel effective CA inhibitors targeting other isoforms with medicinal chemistry applications.

Synthesis of Some Novel Norbornene‐Fused Pyridazines as Potent Inhibitors of Carbonic Anhydrase and Acetylcholinesterase

The reaction of benzocyclic norbornene derivatives with tetrazines provided the 1,3‐dihydropyridazine derivatives as a single product. The dihydropyridazine derivatives have been dehydrogenated with phenyliodine bis(trifluoroacetate) to yield the corresponding pyridazines in a high yield. Two stable diazines, primary product of corresponding 1,4‐dihydropyridazine, were also isolated. Structures were then determined by 1H‐NMR, and 13C‐NMR beside to elemental analyses. The novel pyridazine derivatives (8, 9) efficiently inhibited the cytosolic human carbonic anhydrase isoenzymes I and II (hCA I and II). In addition, these novel pyridazine derivatives (8, 9) were evaluated for their in vitro acetylcholinesterase inhibitory activity. Ligand–receptor interactions are tested using molecular docking simulations. Obtained docking scores are in good agreement with in vitro results.

Carbonic anhydrase inhibitors: Design, synthesis, kinetic, docking and molecular dynamics analysis of novel glycine and phenylalanine sulfonamide derivatives

The inhibition of two human cytosolic carbonic anhydrase isozymes I and II, with some novel glycine and phenylalanine sulfonamide derivatives were investigated. Newly synthesized compounds G1–4 and P1–4 showed effective inhibition profiles with KI values in the range of 14.66–315μM for hCA I and of 18.31–143.8μM against hCA II, respectively. In order to investigate the binding mechanisms of these inhibitors, in silico docking studies were applied. Atomistic molecular dynamic simulations were performed for docking poses which utilize to illustrate the inhibition mechanism of used inhibitors into active site of CAII. These sulfonamide containing compounds generally were competitive inhibitors with 4-nitrophenylacetate as substrate. Some investigated compounds here showed effective hCA II inhibitory effects, in the same range as the clinically used sulfonamide, sulfanilamide or mafenide and might be used as leads for generating enzyme inhibitors possibly targeting other CA isoforms which have not been yet assayed for their interactions with such agents.

Synthesis and carbonic anhydrase inhibitory properties of novel uracil derivatives.

Carbonic anhydrase (CA) inhibitors are valuable molecules based on several therapeutic applications, including antiglaucoma activity. In the present study, inhibition of two human cytosolic carbonic anhydrase isozymes I and II with some uracil derivatives (3-9) were investigated. Compounds 3-9 showed KI values in the range of 10.83-464 μM for hCA I and of 28.88-778.5 μM against hCA II, respectively. Kinetic investigations showed that similarly to classical CA inhibitors, all investigated natural compounds act as competitive inhibitors with 4-NPA as substrate. Uracil derivatives investigated here are promising agents which may be used as lead molecules in order to derivative novel carbonic anhydrase inhibitors that might be useful in medical applications.

N-Acylsulfonamides strongly inhibit human carbonic anhydrase isoenzymes I and II

Sulfonamides represent a significant class of biologically active compounds that inhibit carbonic anhydrase (CA, EC.: 4.2.1.1) isoenzymes involved in different pathological and physiological events. Sulfonamide CA inhibitors are used therapeutically as diuretic, antiglaucoma, antiobesity and anticancer agents. A series of new sulfonamides were synthesized using imides and tosyl chloride as starting materials. These N-acylsulfonamides efficiently inhibited the cytosolic human carbonic anhydrase isoenzymes I, and II (hCA I, and II), with nanomolar range inhibition constants ranging between 36.4±6.0–254.6±18.0 and 58.3±0.6–273.3±2.5nM, respectively.

Synthesis of 3,4-dihydroxypyrrolidine-2,5-dione and 3,5-dihydroxybenzoic acid derivatives and evaluation of the carbonic anhydrase I and II inhibition

The inhibition of two human cytosolic carbonic anhydrase (hCA, EC 4.2.1.1) isozymes I and II, with some 3,4-dihydroxypyrrolidine-2,5-dione and 3,5-dihydroxybenzoic acid derivatives, were investigated by using the esterase assay, with 4-nitrophenyl acetate (4-NPA) as substrate. Compounds 10–13 showed KI values in the range of 112.7–441.5 μM for hCA I and of 3.5–10.76 μM against hCA II, respectively. These hydroxyl group containing compounds generally were competitive inhibitors. Some hydroxyl group containing compounds investigated here showed effective hCA II inhibitory effects, in the same range as the clinically used sulfonamide acetazolamide, and might be used as leads for generating enzyme inhibitors possibly targeting other CA isoforms which have not been yet assayed for their interactions with such agents.

Synthesis of sulfonamides with effective inhibitory action against Porphyromonas gingivalis γ-carbonic anhydrase

New benzenesulfonamides incorporating GABA or N-α-acetyl-l-lysine scaffolds as well as guanidine functionalities as water solubilizing moieties were obtained, using 4-aminoethyl/methyl-benzenesulfonamide and metanilamide/sulfanilamide as zinc-binding motives. The new compounds were medium potency inhibitors of the widespread cytosolic human carbonic anhydrase (CA, EC 4.2.1.1) isoforms I and II and more effective inhibitors (KIs low nanomolar range) of the bacterial γ-CA from the oral pathogen Porphyromonas gingivalis. These sulfonamides may be useful tools for understanding the physiological role of bacterial CAs in pathogenesis of some infectious disease.