Sulfonamide inhibition studies of the β-carbonic anhydrase from the newly discovered bacterium Enterobacter sp. B13

The genome of the newly identified bacterium Enterobacter sp. B13 encodes for a β-class carbonic anhydrases (CAs, EC 4.2.1.1), EspCA. This enzyme was recently cloned, and characterized kinetically by this group (J. Enzyme Inhib. Med. Chem. 2016, 31). Here we report an inhibition study with sulfonamides and sulfamates of this enzyme. The best EspCA inhibitors were some sulfanylated sulfonamides with elongated molecules, metanilamide, 4-aminoalkyl-benzenesulfonamides, acetazolamide, and deacetylated methazolamide (KIs in the range of 58.7-96.5nM). Clinically used agents such as methazolamide, ethoxzolamide, dorzolamide, brinzolamide, benzolamide, zonisamide, sulthiame, sulpiride, topiramate and valdecoxib were slightly less effective inhibitors (KIs in the range of 103-138nM). Saccharin, celecoxib, dichlorophenamide and many simple benzenesulfonamides were even less effective as EspCA inhibitors, with KIs in the range of 384-938nM. Identification of effective inhibitors of this bacterial enzyme may lead to pharmacological tools useful for understanding the physiological role(s) of the β-class CAs in bacterial pathogenicity/virulence.

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.

Dendrimers incorporating benzenesulfonamide moieties strongly inhibit carbonic anhydrase isoforms I-XIV

As extension of our previous study herein we report a comprehensive investigation of poly(amidoamine) (PAMAM) dendrimers as modulators of the human carbonic anhydrase (hCA, EC 4.2.1.1) isoforms I-XIV. Interestingly inhibitory activity was observed for the non-functionalized dendrimers against the hCA I, VII, IX, XII and XIV isoforms, whereas activation properties were reported only for the cytosolic abundant hCA II. Highly efficient inhibitory action against many isoforms having medicinal chemistry applications, such as hCA II, V, VII, IX, XII and XIV, was observed for the PAMAM functionalized counterparts bearing 4, 8, 16 and 32 benzenesulfonamide moieties. Possible applications of dendrimer-CA inhibitors as therapeutic/diagnostic agents are envisaged.

Poly(amidoamine) Dendrimers with Carbonic Anhydrase Inhibitory Activity and Antiglaucoma Action

Four generations of poly(amidoamine) (PAMAM) dendrimers decorated with benzenesulfonamide moieties were prepared by derivatizing the amino groups of the dendrimer with 4-carboxy-benzenesulfonamide functionalities. Compounds incorporating 4, 8, 16, and 32 sulfonamide moieties were thus obtained, which showed an increasing carbonic anhydrase (CA, EC 4.2.1.1) inhibitory action with the increase of the number of sulfamoyl groups in the dendrimer. Best inhibitory activity (in the low nanomolar-subnanomolar range) was observed for isoforms CA II and XII, involved among others in glaucoma. In an animal model of this disease, the chronic administration of such dendrimers for 5 days led to a much more efficient drop of intraocular pressure compared to the standard drug dorzolamide.

Synthesis, characterization, antimicrobial activity and carbonic anhydrase enzyme inhibitor effects of salicilaldehyde-N-methyl p-toluenesulfonylhydrazone and its Palladium(II), Cobalt(II) complexes

We report the synthesis of the ligand, salicilaldehyde-N-methyl p-toluenesulfonylhydrazone (salptsmh) derived from p-toluenesulfonicacid-1-methylhydrazide (ptsmh) and its Pd(II) and Co(II) metal complexes were synthesized for the first time. The structure of the ligand and their complexes were investigated using elemental analysis, magnetic susceptibility, molar conductance and spectral (IR, NMR and LC-MS) measurements. Salptsmh has also been characterized by single crystal X-ray diffraction. (1)H and (13)C shielding tensors for crystal structure were calculated with GIAO/DFT/B3LYP/6-311++G(d,p) methods in CDCl3. The complexes were found to have general composition [ML2]. The results of elemental analysis showed 1:2 (metal/ligand) stoichiometry for all the complex. Magnetic and spectral data indicate a square planar geometry for Pd(II) complex and a distorted tetrahedral geometry for Co(II) complexes. The ligand and its metal chelates have been screened for their antimicrobial activities using the disk diffusion method against the selected Gram positive bacteria: Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, Enterococcus faecalis, Gram negative bacteria: Eschericha coli, Pseudomonas aeruginosa, Klebsiella pneumonia. The inhibition activities of these compounds on carbonic anhydrase II (CA II) and carbonic anhydrase I (CA I) have been investigated by comparing IC50 and Ki values and it has been found that Pd(II) complex have more enzyme inhibition efficiency than salptsmh and Co(II) complex.

Synthesis and in vitro inhibition effect of new pyrido[2,3-d]pyrimidine derivatives on erythrocyte carbonic anhydrase I and II

In vitro inhibition effects of indolylchalcones and new pyrido[2,3-d]pyrimidine derivatives on purified human carbonic anhydrase I and II (hCA I and II) were investigated by using CO2 as a substrate. The results showed that all compounds inhibited the hCA I and hCA II enzyme activities. Among all the synthesized compounds, 7e (IC50 = 6.79 µM) was found to be the most active compound for hCA I inhibitory activity and 5 g (IC50 = 7.22 µM) showed the highest hCA II inhibitory activity. Structure-activity relationships study showed that indolylchalcone derivatives have higher inhibitory activities than pyrido[2,3-d]pyrimidine derivatives on hCA I and hCA II. Additionally, methyl group bonded to uracil ring increases inhibitory activities on both hCA I and hCA II.

Identification two novel nacrein-like proteins involved in the shell formation of the Pacific oyster Crassostrea gigas

Nacrein-like proteins have carbonic anhydrase (CA)-like domains, but their coding regions are flanked by inserted repeat sequence, such as Gly-X-Asn. Reportedly, nacrein-like proteins show the highest similarity to human carbonic anhydrase 1(α-CA1), possess CA catalytic functions, and play a key role in shell biomineralization. In the present study, two novel nacrein-like proteins were firstly identified from the shell-forming mantle of the Pacific oyster Crassostrea gigas. With numerous analyses, it was identified and characterized that both the nacrein-like proteins F1 and F2 were secreted and most closely related to the nacrein-like protein of California mussel Mytilus californianus via phylogenetic analysis. RT-PCR analysis showed that the nacrein-like proteins F1 and F2 were expressed in multiple tissues and the expression levels remarkably rose after entering the spat stage, which were basically consistent with the increase of calcite fractions in the total shell volume. Surprisingly, the Gly-X-Asn repeat domain, which is distinctive in most nacrein-like proteins, was absent in the two newly identified nacrein-like proteins in C. gigas and replaced with a series of acidic amino acids (D/E). Regardless, nacrein-like proteins in mollusks seem to be vital to the deposition of calcium carbonate and likely perform diverse functions.

Carbonic anhydrase inhibitors: synthesis and inhibition of the human carbonic anhydrase isoforms I, II, IX and XII with benzene sulfonamides incorporating 4- and 3-nitrophthalimide moieties

A series of 4 and 5 nitro-1,3-dioxoisoindolin-2-yl benzenesulfonamide derivatives (compounds 1-8) was synthesized by reaction of benzenesulfonamide derivatives with 4 and 3-nitrophthalic anhydrides. These new sulfonamides were investigated as inhibitors of the zinc metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) and more specifically against the human (h) cytosolic isoforms hCA I and II and the transmembrane, tumor-associated hCA IX and XII. Most of the novel compounds were medium potency-weak hCA I inhibitors (Kis in the range of 295-10,000 nM), but were more effective hCA II inhibitors (Kis of 1.7-887 nM). The tumor-associated hCA IX was also inhibited, with Kis in the micromolar range, whereas against hCA XII the inhibition constants were in the range of 90-3,746 nM. The structure-activity relationship (SAR) with this series of sulfonamides is straightforward, with the main features leading to good activity for each isoforms being established. The high sequence hCA alignment homology and molecular docking studies was performed in order to rationalize the activities reported and binding mode to different hCA as inhibitors.

Structural study of the location of the phenyl tail of benzene sulfonamides and the effect on human carbonic anhydrase inhibition

The crystal structure of 4-phenylacetamidomethyl-benzenesulfonamide (4ITP) bound to human carbonic anhydrase (hCA, EC 4.2.1.1) II is reported. 4ITP is a medium potency hCA I and II inhibitor (KIs of 54-75nM), a strong mitochondrial CA VA/VB inhibitor (KIs of 8.3-8.6nM) and a weak transmembrane CA inhibitor (KIs of 136-212nM against hCA IX and XII). This elongated compound binds in an extended conformation to hCA II, with its tail lying towards the hydrophobic half of the active site whereas the sulfonamide moiety coordinates the zinc ion. The present structure was compared to that of structurally related aromatic sulfonamides, such as 4-phenylacetamido-benzene-sulfonamide (3OYS), 4-(2-mercaptophenylacetamido)-benzene-sulfonamide (2HD6) and 4-(3-nitrophenyl)-ureido-benzenesulfonamide (3N2P). Homology models of the hCA I, VA, VB, IX and XII structures were build which afforded an understanding of the amino acids involved in the binding of these compounds to these isoforms. The main conclusion of the study is that the orientation of the tail moiety and the presence of flexible linkers as well polar groups in it, strongly influence the potency and the selectivity of the sulfonamides for the inhibition of cytosolic, mitochondrial or transmembrane CA isoforms.

Carbonic anhydrase inhibitors: Synthesis and inhibition of the cytosolic mammalian carbonic anhydrase isoforms I, II and VII with benzene sulfonamides incorporating 4,5,6,7-tetrachlorophthalimide moiety

A series of 4,5,6,7-tetrachloro-1,3-dioxoisoindolin-2-yl benzenesulfonamide derivatives (compounds 1-8) was synthesized by reaction of benzene sulfonamides incorporating primary amino moieties with 4,5,6,7-tetrachlorophthalic anhydride. These sulfonamides were assayed as inhibitors of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1). Some of these compounds showed very good in vitro human carbonic anhydrase (hCA) isoforms I, II and VII inhibitory properties, with affinities in the low nanomolar range. Inhibition activities against hCA I were in the range of 159-444nM; against hCA II in the range of 2.4-4515nM, and against hCA VII in the range of 1.3-469nM. The structure-activity relationship (SAR) with this series of sulfonamides is straightforward, with the main features leading to good activity for each isoform being established.

Design and synthesis of novel 4-(4-oxo-2-arylthiazolidin-3-yl)benzenesulfonamides as selective inhibitors of carbonic anhydrase IX over I and II with potential anticancer activity

The novel 4-(4-oxo-2-arylthiazolidin-3-yl)benzenesulfonamide derivatives were designed and synthesized for selective carbonic anhydrase IX (CA IX) inhibitory activity with anticancer potential. In the CA inhibition assay, 3f was found to be the most potent and selective inhibitor of CA IX with inhibitory constant (K(I)) value of 2.2 nM. Among the synthesized compounds, 3f showed IC₅₀ values of 5.03 μg/ml (cisplatin: 6.56 μg/ml), 5.81 μg/ml (cisplatin: 5.85 μg/ml), and 23.93 μg/ml (cisplatin: 2.75 μg/ml) against COLO-205, MDA-MB-231, and DU-145 cell lines, respectively. At IC₅₀, 3f caused cell shrinkage, nuclear condensation, and nuclear fragmentation events characteristic to apoptosis in the Hoechst 33258 and acridine orange-ethidium bromide staining studies of COLO-205 cells. In the Dalton's lymphoma ascites (DLA) solid tumor model 3f decreased tumor volume by 64.83% (cisplatin: 71.62%), while increase in mean body weight was found to be only 4.09% (cisplatin: 3.47%).

Quantitative comparison of protein dynamics in live cells and in vitro by in-cell (19)F-NMR

Here we describe how a (19)F-probe incorporated into an endogenous protein by a chemical biology method revealed protein dynamics. By explicit determination of ligand-bound and unbound structures with X-ray crystallography, the quantitative comparison of the protein's dynamics in live cells and in vitro is presented. These results clearly demonstrated the greater conformational fluctuations of the intracellular protein, partially due to macromolecular crowding effects.

[Clinicopathological significance of the expression of carbonic anhydrase I and II in human pancreatic cancer]

OBJECTIVE

To explore the clinicopathological significance of the expression of carbonic anhydrase I (CAI) and carbonic anhydrase II (CAII) protein and mRNA levels in pancreatic ductal adenocarcinoma (PDAC).

METHODS

The expression of CAI and CAII protein in 57 pairs of paraffin-embedded PDAC specimens and adjacent non-cancerous pancreatic tissues were detected by immunohistochemistry. The relationship between the protein expression and clinicopathological characters was analyzed. Western blot and quantitative real-time polymerase chain reaction (QRT-PCR) were used to examine the expression of CAI and CAII protein and mRNA levels in 16 paired fresh PDAC specimens, adjacent non-cancerous pancreatic tissues and 3 different differentiated pancreatic cancer cells (PANC-1, BxPC-3 & SW1990).

RESULTS

The expression of CAI protein was higher in PDAC compared with that in paired non-cancerous pancreatic tissues (t = 2.395, P = 0.020), whereas, CAII expression was significantly lower in PDAC than that in paired non-cancerous pancreatic tissues (t = 4.296, P = 0.000). The expression of CAI and CAII protein had a positive correlation with tumor differentiation (χ(2) = 7.557, P = 0.023; χ(2) = 7.822, P = 0.020) and CAI showed a direct negative correlation with vascular invasion (χ(2) = 6.349, P = 0.012). Univariate and multivariate analysis with clinicopathological characters revealed that the CAII expression was an independent prognostic indicator for PDAC patients (P = 0.017; P = 0.011 respectively). No significant difference of CAI mRNA and protein expression existed between PDAC and adjacent normal pancreatic tissues (t = 1.619, P = 0.126; t = 1.352, P = 0.197) as detected by Western blot and QRT-PCR, but the expression of CAII mRNA and protein levels was much lower in PDAC than that in paired non-cancerous pancreatic tissues, respectively (t = 3.360, P = 0.004; t = 2.934, P = 0.010). Moreover, the mRNA and protein expression of CAI and CAII gradually increased with the better differentiation degree of pancreatic cancer cells.

CONCLUSIONS

CAI is up-regulated and CAII down-regulated in PDAC. Both of them are correlated with tumor differentiation. CAII expression is an independent prognostic indicator for PDAC patients.

Transport activity of the sodium bicarbonate cotransporter NBCe1 is enhanced by different isoforms of carbonic anhydrase

Transport metabolons have been discussed between carbonic anhydrase II (CAII) and several membrane transporters. We have now studied different CA isoforms, expressed in Xenopus oocytes alone and together with the electrogenic sodium bicarbonate cotransporter 1 (NBCe1), to determine their catalytic activity and their ability to enhance NBCe1 transport activity. pH measurements in intact oocytes indicated similar activity of CAI, CAII and CAIII, while in vitro CAIII had no measurable activity and CAI only 30% of the activity of CAII. All three CA isoforms increased transport activity of NBCe1, as measured by the transport current and the rate of intracellular sodium rise in oocytes. Two CAII mutants, altered in their intramolecular proton pathway, CAII-H64A and CAII-Y7F, showed significant catalytic activity and also enhanced NBCe1 transport activity. The effect of CAI, CAII, and CAII mutants on NBCe1 activity could be reversed by blocking CA activity with ethoxyzolamide (EZA, 10 µM), while the effect of the less EZA-sensitive CAIII was not reversed. Our results indicate that different CA isoforms and mutants, even if they show little enzymatic activity in vitro, may display significant catalytic activity in intact cells, and that the ability of CA to enhance NBCe1 transport appears to depend primarily on its catalytic activity.

In Vitro inhibition of human carbonic anhydrase I and II isozymes with natural phenolic compounds

Inhibition of two human cytosolic carbonic anhydrase (hCA, EC 4.2.1.1) isozymes I and II with some natural phenolic derivatives was investigated using the esterase assay with 4-nitrophenyl acetate as substrate. Resveratrol, catechin, silymarin, dobutamin, and curcumin showed K(I) values in the range of 4.47-9.47 mm for hCA I and of 2.86-7.44 μm against hCA II, respectively. These natural product phenols were generally competitive inhibitors with 4-nitrophenylacetate as substrate. Some natural phenols 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 that have not been yet assayed for their interactions with such agents.

Altered intestinal epithelial homeostasis in mice with intestine-specific deletion of the Krüppel-like factor 4 gene

The zinc finger transcription factor, Krüppel-like factor 4 (KLF4), is expressed in the post-mitotic, differentiated epithelial cells lining the intestinal tract and exhibits a tumor suppressive effect on intestinal tumorigenesis. Here we report a role for KLF4 in maintaining homeostasis of intestinal epithelial cells. Mice with conditional ablation of the Klf4 gene from the intestinal epithelium were viable. However, both the rates of proliferation and migration of epithelial cells were increased in the small intestine of mutant mice. In addition, the brush-border alkaline phosphatase was reduced as was expression of ephrine-B1 in the small intestine, resulting in mispositioning of Paneth cells to the upper crypt region. In the colon of mutant mice, there was a reduction of the differentiation marker, carbonic anhydrase-1, and failure of differentiation of goblet cells. Mechanistically, deletion of Klf4 from the intestine resulted in activation of genes in the Wnt pathway and reduction in expression of genes encoding regulators of differentiation. Taken together, these data provide new insights into the function of KLF4 in regulating postnatal proliferation, migration, differentiation, and positioning of intestinal epithelial cells and demonstrate an essential role for KLF4 in maintaining normal intestinal epithelial homeostasis in vivo.

Indapamide-like benzenesulfonamides as inhibitors of carbonic anhydrases I, II, VII, and XIII

A series of novel 2-chloro-5-[(1-benzimidazolyl- and 2-benzimidazolylsulfanyl)acetyl]benzene-sulfonamides were designed and synthesized. Their binding to recombinant human carbonic anhydrase (hCA) isozymes I, II, VII, and XIII was determined by isothermal titration calorimetry and thermal shift assay. The designed S-alkylated benzimidazole derivatives exhibited stronger binding than the indapamide-like N-alkylated benzimidazoles, with the K(d) reaching about 50-100 nM with drug-targeted hCAs VII and XIII. The cocrystal structures of selected compounds with hCA II were determined by X-ray crystallography, and structural features of the binding event were revealed.

4-[N-(substituted 4-pyrimidinyl)amino]benzenesulfonamides as inhibitors of carbonic anhydrase isozymes I, II, VII, and XIII

A series of 4-[N-(substituted 4-pyrimidinyl)amino]benzenesulfonamides were designed and synthesised. Their binding potencies as inhibitors of selected recombinant human carbonic anhydrase (hCA) isozymes I, II, VII, and XIII were measured using isothermal titration calorimetry and the thermal shift assay. To determine the structural features of inhibitor binding, the crystal structures of several compounds in complex with hCA II were determined. Several compounds exhibited selectivity towards isozymes I, II, and XIII, and some were potent inhibitors of hCA VII.

Carbonic anhydrases are upstream regulators of CO2-controlled stomatal movements in guard cells

The continuing rise in atmospheric CO2 causes stomatal pores in leaves to close and thus globally affects CO2 influx into plants, water use efficiency and leaf heat stress. However, the CO2-binding proteins that control this response remain unknown. Moreover, which cell type responds to CO2, mesophyll or guard cells, and whether photosynthesis mediates this response are matters of debate. We demonstrate that Arabidopsis thaliana double-mutant plants in the beta-carbonic anhydrases betaCA1 and betaCA4 show impaired CO2-regulation of stomatal movements and increased stomatal density, but retain functional abscisic-acid and blue-light responses. betaCA-mediated CO2-triggered stomatal movements are not, in first-order, linked to whole leaf photosynthesis and can function in guard cells. Furthermore, guard cell betaca-overexpressing plants exhibit instantaneous enhanced water use efficiency. Guard cell expression of mammalian alphaCAII complements the reduced sensitivity of ca1 ca4 plants, showing that carbonic anhydrase-mediated catalysis is an important mechanism for betaCA-mediated CO2-induced stomatal closure and patch clamp analyses indicate that CO2/HCO3- transfers the signal to anion channel regulation. These findings, together with ht1-2 (ref. 9) epistasis analysis demonstrate that carbonic anhydrases function early in the CO2 signalling pathway, which controls gas-exchange between plants and the atmosphere.

Different effects of L-arginine on protein refolding: suppressing aggregates of hydrophobic interaction, not covalent binding

Arginine is one of the most favorable additives in protein refolding. However, arginine does not work for certain disulfide-bond-containing proteins, which is not yet well explained. In this work, refolding of three proteins in the presence of 0-2 M arginine was investigated and compared. Bovine carbonic anhydrase B (CAB), containing no cysteine, was successfully refolded with the help of arginine. The refolding yield could reach almost 100% in the presence of 0.75 M arginine. However, recombinant human colony stimulating factor (rhG-CSF), containing five cysteines, could only achieve 65% refolding yield. The formation of aggregates was found. Blocking of free SH groups of the denatured rhG-CSF by iodoacetamide and subsequently refolding of the protein could reduce the aggregate formation substantially. Further investigation on recombinant green fluorescence protein (GFP), containing two cysteines, also revealed the accumulation of oligomers. The content of oligomers increased with the concentration of arginine, reaching about 30% at 2 M arginine. Comparison of reduced and nonreduced SDS-PAGE revealed that the oligomers were formed through intermolecular disulfide binding. Analysis of the refolding kinetics indicated that intermolecular disulfide bonds were probably formed in the intermediate stage where arginine slowed down the refolding rate and stabilized the intermediates. The accumulated intermediates with unpaired cysteine possessed more chances to react with each other to form oligomers, whereas arginine failed to inhibit disulfide bond formation.

Cryptophane xenon-129 nuclear magnetic resonance biosensors targeting human carbonic anhydrase

(129)Xe NMR biosensors are promising agents for early disease detection, especially when their interactions with target biomolecules can perturb (129)Xe chemical shifts well beyond the typical field inhomogeneity of clinical MRI. We introduce human carbonic anhydrase (CA) as a single-binding-site enzyme for studying xenon biosensor-protein interactions. A xenon-binding cryptophane was substituted with linkers of varying lengths to p-benzenesulfonamide to yield nondiastereomeric biosensors with a single (129)Xe NMR resonance. X-ray crystallography confirmed binding of the eight-bond-linked biosensor containing a single xenon atom in the CAII active site. Biosensor dissociation constants (K(d) = 20-110 nM) were determined by isothermal titration calorimetry (ITC) for isozymes CA I and II. The biosensor-CA complexes yielded "bound" hyperpolarized (129)Xe NMR resonances of narrow line width that were shifted by 3.0-7.5 ppm downfield, signifying much larger shifts than seen previously. Moreover, isozyme-specific chemical shifts clearly differentiated CA I and II, despite their similar structures. Thus, xenon biosensors may provide a powerful strategy for diagnosing human diseases characterized by the upregulation of specific CA isozymes and other protein biomarkers.

Carbonic Anhydrase Inhibitors. Inhibition of Cytosolic Isozymes I and II and Transmembrane, Cancer-associated Isozyme IX with Lipophilic Sulfonamides

A series of new compounds was obtained by reaction of aromatic/heterocyclic sulfonamides incorporating amino groups with N,N-diphenylcarbamoyl chloride and diphenylacetyl chloride. These sulfonamides were assayed for the inhibition of three carbonic anhydrase (CA, EC 4.2.1.1) isozymes: the cytosolic CA I and CA II, and the transmembrane, cancer-associated isozyme CA IX. Good inhibitors against all these isoforms were detected, and the inhibition profile of the newly investigated isozyme IX was observed to be different from that of the cytosolic isozymes, I and II. This may lead to the development of novel anticancer therapies based on the selective inhibition of CA IX.

Carbonic Anhydrase Inhibitors: Aliphatic N-phosphorylated Sulfamates--A Novel Zinc-anchoring Group Leading to Nanomolar Inhibitors

A small library of phosphorylated sulfamates (N-(O-alkylsulfamoyl)-phosphoramidic acids) incorporating long aliphatic chains (C8-C16) has been synthesized and investigated for their interaction with two physiologically relevant carbonic anhydrase (CA) isozymes. These compounds behaved as very potent inhibitors of both isozymes, with inhibition constants in the range of 8.2-16.1nM against isozyme hCA I, and 5.3-11.9nM against isozyme hCA II. Activity was optimal for the n-octyl derivative (similarly with that of the corresponding unsubstituted sulfamates) and gradually decreased for the longer chain derivatives. Some of these compounds are much more effective CA inhibitors as compared to the clinically used derivatives acetazolamide, sulfanilamide or topiramate, which are used as standards for the enzymatic determinations. The phosphorylated sulfamate moiety represents a novel zinc-binding group for the design of effective CA inhibitors.

Carbonic Anhydrase Inhibitors: Schiff's Bases of Aromatic and Heterocyclic Sulfonamides and their Metal Complexes

Schiff's bases were obtained from aromatic/heterocyclic sulfonamides and amino-sulfonamide derivatives, such as sulfanilamide, homosulfanilamide, 4-aminoethyl-benzenesulfonamide and 5-amino-1,3,4-thiadiazole-2-sulfonamide. Metal complexes of some of these Schiff's bases, incorporating Zn(II), Co(lI), Ni(II) and Cu(II) ions, were also prepared and tested as inhibitors of the zinc enzyme carbonic anhydrase (CA), and more specifically the red blood cell isozymes I and II. The Schiff's bases behaved as medium potency CA I and CA II inhibitors, whereas their metal complexes showed a highly enhanced potency, with several low nanomolar CA II inhibitors detected.

Quantitative Structure Activity Relationship Studies of Sulfamide Derivatives as Carbonic Anhydrase Inhibitor: As Antiglaucoma Agents

Selective inhibition of ciliary process enzyme i.e. Carbonic Anhydrase-II is an excellent approach in reducing elevated intraocular pressure, thus treating glaucoma. Due to characteristic physicochemical properties of sulphonamide (Inhibition of Carbonic Anhydrase), they are clinically effective against glaucoma. But the non-specificity of sulphonamide derivatives to isozyme, leads to a range of side effects. Presently, the absence of comparative studies related to the binding of the sulphonamides as inhibitors to CA isozymes limits their use. In this paper we have represented "Three Dimensional Quantitative Structure Activity Relationship" study to characterize structural features of Sulfamide derivative [RR'NSO(2)NH(2)] as inhibitors, that are required for selective binding of carbonic anhydrase isozymes (CAI and CAII). In the analysis, stepwise multiple linear regression was performed using physiochemical parameters as independent variable and CA-I and CA-II inhibitory activity as dependent variable, respectively. The best multiparametric QSAR model obtained for CA-I inhibitory activity shows good statistical significance (r= 0.9714) and predictability (Q(2)=0.8921), involving the Electronic descriptors viz. Highest Occupied Molecular Orbital, Lowest Unoccupied Molecular Orbital and Steric descriptors viz. Principal moment of Inertia at X axis. Similarly, CA-II inhibitory activity also shows good statistical significance (r=0.9644) and predictability (Q(2)=0.8699) involving aforementioned descriptors. The predictive power of the model was successfully tested externally using a set of six compounds as test set for CA-I inhibitory activity and a set of seven compounds in case of CA-II inhibitory activity with good predictive squared correlation coefficient, r(2)(pred)=0.6016 and 0.7662, respectively. Overview of analysis favours substituents with high electronegativity and less bulk at R and R' positions of the parent nucleus, provides a basis to design new Sulfamide derivatives possessing potent and selective carbonic anhydrase-II inhibitory activity.