Predicting sulfanilamide solubility in the binary mixtures using a reference solvent approach.

BACKGROUND: Solubility is a fundamental physicochemical property of active pharmaceutical ingredients. The optimization of a dissolution medium aims not only to increase solubility and other aspects are to be included such as environmental impact, toxicity degree, availability, and costs. Obtaining comprehensive solubility characteristics of chemical compounds is a non-trivial and demanding process. Therefore, support from theoretical approaches is of practical importance. OBJECTIVES: This study aims to examine the accuracy of the reference solubility approach in the case of sulfanilamide dissolution in a variety of binary solvents. This pharmaceutically active substance has been extensively studied, and a substantial amount of solubility data is available. Unfortunately, using this set of data directly for theoretical modeling is impeded by noticeable inconsistencies in the published solubility data. Hence, this aspect is addressed by data curation using theoretical and experimental confirmations. MATERIAL AND METHODS: In the experimental part of our study, the popular shake-flask method combined with ultraviolet (UV) spectrophotometric measurements was applied for solubility determination. The computational phase utilized the conductor-like screening model for real solvents (COSMO-RS) approach. RESULTS: The analysis of the results of solubility calculations for sulfonamide in binary solvents revealed abnormally high error values for acetone-ethyl acetate mixtures, which were further confirmed with experimental measurements. Additional confirmation was obtained by extending the solubility measurements to a series of homologous acetate esters. CONCLUSIONS: Our study addresses the crucial issue of coherence of solubility data used for many theoretical inquiries, including parameter fitting of semi-empirical models, in-depth thermodynamic interpretations and application of machine learning protocols. The effectiveness of the proposed methodology for dataset curation was demonstrated for sulfanilamide solubility in binary mixtures. This approach enabled not only the formulation of a consistent dataset of sulfanilamide solubility binary solvent mixtures, but also its implementation as a qualitative tool guiding rationale solvent selection for experimental solubility screening.

Structure and substrate specificity determinants of NfnB, a dinitroaniline herbicide-catabolizing nitroreductase from Sphingopyxis sp. strain HMH.

Nitroreductases are emerging as attractive bioremediation enzymes, with substrate promiscuity toward both natural and synthetic compounds. Recently, the nitroreductase NfnB from Sphingopyxis sp. strain HMH exhibited metabolic activity for dinitroaniline herbicides including butralin and pendimethalin, triggering the initial steps of their degradation and detoxification. However, the determinants of the specificity of NfnB for these herbicides are unknown. In this study, we performed structural and biochemical analyses of NfnB to decipher its substrate specificity. The homodimer NfnB is a member of the PnbA subgroup of the nitroreductase family. Each monomer displays a central α + ß fold for the core domain, with a protruding middle region and an extended C-terminal region. The protruding middle region of Val75-Tyr129 represents a structural extension that is a common feature to members of the PnbA subgroup and functions as an opening wall connecting the coenzyme FMN-binding site to the surface, therefore serving as a substrate binding site. We performed mutational, kinetic, and structural analyses of mutant enzymes and found that Tyr88 in the middle region plays a pivotal role in substrate specificity by determining the dimensions of the wall opening. The mutation of Tyr88 to phenylalanine or alanine caused significant changes in substrate selectivity toward bulkier dinitroaniline herbicides such as oryzalin and isopropalin without compromising its activity. These results provide a framework to modify the substrate specificity of nitroreductase in the PnbA subgroup, which has been a challenging issue for its biotechnological and bioremediation applications.

Synthesis and cytotoxic activities of novel copper and silver complexes of 1,3-diaryltriazene-substituted sulfonamides.

In this study, a series of 10 novel copper (II) and silver complexes of 1,3-diaryltriazene-substituted sulfonamides was synthesised. All the synthesised ligands and their metal complexes were assessed for in vitro cytotoxicity against human colorectal adenocarcinoma (DLD-1), cervix carcinoma (HeLa), breast adenocarcinoma (MDA-MB-231), colon adenocarcinoma (HT-29), endometrial adenocarcinoma (ECC-1), prostate cancer (DU-145 and PC-3), normal embryonic kidney (HEK-293), normal prostate epithelium (PNT-1A), and normal retinal pigment epithelium (ARPE-19) cells. Most of the metal complexes from the series showed to be more active against all cancerous cells than the uncomplexed 1,3-diaryltriazene-substituted sulfonamides, and lower cytotoxic effects observed on normal cells. Most of the Cu (II) and Ag (I) metal complexes from the presented series showed high cytotoxic activity against HeLa cells with IC50 values ranging from 2.08 to >300 µM. Specifically, compound L3-Ag showed one of the highest cytotoxicity against all cancer cell lines with IC50 values between 3.30 to 16.18 µM among other tested compounds.

Target-based drug discovery through inversion of quantitative structure-drug-property relationships and molecular simulation: CA IX-sulphonamide complexes.

In this work, a target-based drug screening method is proposed exploiting the synergy effect of ligand-based and structure-based computer-assisted drug design. The new method provides great flexibility in drug design and drug candidates with considerably lower risk in an efficient manner. As a model system, 45 sulphonamides (33 training, 12 testing ligands) in complex with carbonic anhydrase IX were used for development of quantitative structure-activity-lipophilicity (property)-relationships (QSPRs). For each ligand, nearly 5,000 molecular descriptors were calculated, while lipophilicity (logkw) and inhibitory activity (logKi) were used as drug properties. Genetic algorithm-partial least squares (GA-PLS) provided a QSPR model with high prediction capability employing only seven molecular descriptors. As a proof-of-concept, optimal drug structure was obtained by inverting the model with respect to reference drug properties. 3509 ligands were ranked accordingly. Top 10 ligands were further validated through molecular docking. Large-scale MD simulations were performed to test the stability of structures of selected ligands obtained through docking complemented with biophysical experiments.

Novel thiazolidinone-containing compounds, without the well-known sulphonamide zinc-binding group acting as human carbonic anhydrase IX inhibitors.

A small collection of 26 structurally novel thiazolidinone-containing compounds, without the well-known sulphonamide zinc-binding group, were synthesised and tested in enzyme inhibition assays against the tumour-associated hCA IX enzyme. Inhibition constants in the lower micromolar region (KI < 25 µM) have been measured for 17 of the 26 compounds. Even though the KI values are relatively weak, the fact that they do not contain a sulphonamide moiety suggests that these compounds do not interact with the active site zinc ion. Therefore, docking studies and molecular dynamics simulations have been performed to suggest binding poses for these structurally novel inhibitors.

Fungal biofilm inhibition by piperazine-sulphonamide linked Schiff bases: Design, synthesis, and biological evaluation.

We report the synthesis of some new piperazine-sulphonamide linked Schiff bases as fungal biofilm inhibitors with antibacterial and antifungal potential. The biofilm inhibition result of Candida albicans proposed that the compounds 6b (IC50 = 32.1 µM) and 6j (IC50 = 31.4 µM) showed higher inhibitory activity than the standard fluconazole (IC50 = 40 µM). Compound 6d (MIC = 26.1 µg/mL) with a chloro group at the para position was found to be the most active antibacterial agent of the series against Bacillus subtilis when compared with the standard ciprofloxacin (MIC = 50 µg/mL). Compound 6j (MIC = 39.6 µg/mL) with an OH group at the ortho position showed more potent antifungal activity as compared to that of the standard fluconazole (IC50 = 50 µM) against C. albicans. Thus, the synthesized compounds 6a-k were found to be potent biofilm inhibitors as well as active antibacterial and antifungal agents. The molecular docking study of the synthesized compounds against the secreted aspartyl protease (SAP5) enzyme of C. albicans exhibited good binding properties. The in silico ADME properties of the synthesized compounds were also analyzed and showed their potential to be developed as potential oral drug candidates.

Design and Comparative Evaluation of the Anticonvulsant Profile, Carbonic-Anhydrate Inhibition and Teratogenicity of Novel Carbamate Derivatives of Branched Aliphatic Carboxylic Acids with 4-Aminobenzensulfonamide.

Epilepsy is one of the most common neurological diseases, with between 34 and 76 per 100,000 people developing epilepsy annually. Epilepsy therapy for the past 100+ years is based on the use of antiepileptic drugs (AEDs). Despite the availability of more than twenty old and new AEDs, approximately 30% of patients with epilepsy are not seizure-free with the existing medications. In addition, the clinical use of the existing AEDs is restricted by their side-effects, including the teratogenicity associated with valproic acid that restricts its use in women of child-bearing age. Thus, there is an unmet clinical need to develop new, effective AEDs. In the present study, a novel class of carbamates incorporating phenethyl or branched aliphatic chains with 6-9 carbons in their side-chain, and 4-benzenesulfonamide-carbamate moieties were synthesized and evaluated for their anticonvulsant activity, teratogenicity and carbonic anhydrase (CA) inhibition. Three of the ten newly synthesized carbamates showed anticonvulsant activity in the maximal-electroshock (MES) and 6 Hz tests in rodents. In mice, 3-methyl-2-propylpentyl(4-sulfamoylphenyl)carbamate(1), 3-methyl-pentan-2-yl-(4-sulfamoylphenyl)carbamate (9) and 3-methylpentyl, (4-sulfamoylphenyl)carbamate (10) had ED50 values of 136, 31 and 14 mg/kg (MES) and 74, 53, and 80 mg/kg (6 Hz), respectively. Compound (10) had rat-MES-ED50 = 13 mg/kg and ED50 of 59 mg/kg at the mouse-corneal-kindling test. These potent carbamates (1,9,10) induced neural tube defects only at doses markedly exceeding their anticonvuslnat-ED50 values. None of these compounds were potent inhibitors of CA IV, but inhibited CA isoforms I, II and VII. The anticonvulsant properties of these compounds and particularly compound 10 make them potential candidates for further evaluation and development as new AEDs.

Identification of selective 8-(piperidin-4-yloxy)quinoline sulfone and sulfonamide histamine H1 receptor antagonists for use in allergic rhinitis.

A series of potent, selective and long-acting quinoline-based sulfonamide human H1 histamine receptor antagonists, designed for once-daily intranasal administration for the treatment of rhinitis were developed. Sulfonamide 33b had a slightly lower affinity for the H1 receptor than azelastine, had low oral bioavailability in the rat and dog, and was turned over to five major metabolites. Furthermore, 33b had longer duration of action than azelastine in guinea pigs, lower rat brain-penetration, and did not cause time dependent inhibition of CYP2D6 or CYP3A4. The clinical dose in humans is expected to be low (approximately 0.5mg per day) based on the clinical dose used for azelastine and a comparison of efficacy data from animal models for 33b and azelastine.

Laser desorption single-conformation UV and IR spectroscopy of the sulfonamide drug sulfanilamide, the sulfanilamide-water complex, and the sulfanilamide dimer.

We have studied the conformational preferences of the sulfonamide drug sulfanilamide, its dimer, and its monohydrated complex through laser desorption single-conformation UV and IR spectroscopy in a molecular beam. Based on potential energy curves for the inversion of the anilinic and the sulfonamide NH2 groups calculated at DFT level, we suggest that the zero-point level wave function of the sulfanilamide monomer is appreciably delocalized over all four conformer wells. The sulfanilamide dimer, and the monohydrated complex each exhibit a single isomer in the molecular beam. The isomeric structures of the sulfanilamide dimer and the monohydrated sulfanilamide complex were assigned based on their conformer-specific IR spectra in the NH and OH stretch region. Quantum Theory of Atoms in Molecules (QTAIM) analysis of the calculated electron density in the water complex suggests that the water molecule is bound side-on in a hydrogen bonding pocket, donating one O-HO[double bond, length as m-dash]S hydrogen bond and accepting two hydrogen bonds, a NHO and a CHO hydrogen bond. QTAIM analysis of the dimer electron density suggests that the Ci symmetry dimer structure exhibits two dominating N-HO[double bond, length as m-dash]S hydrogen bonds, and three weaker types of interactions: two CHO bonds, two CHN bonds, and a chalcogen OO interaction. Most interestingly, the molecular beam dimer structure closely resembles the R dimer unit - the dimer unit with the greatest interaction energy - of the α, γ, and δ crystal polymorphs. Interacting Quantum Atoms analysis provides evidence that the total intermolecular interaction in the dimer is dominated by the short-range exchange-correlation contribution.

Herbicide oryzalin inhibits human carbonic anhydrases in vitro.

Herbicides of the dinitroaniline chemical class, widely used oryzalin and trifluralin, and also nitralin were tested as inhibitors of recombinant human carbonic anhydrases (CAs). Oryzalin bound and inhibited 11 out of 12 catalytically active CA isoforms present in the human body with the affinities in the same range as clinically used CA drugs, while no effect was detected for the other two compounds. Binding of all three herbicides was examined by fluorescence-based thermal shift assay, isothermal titration calorimetry, and the inhibition of carbon dioxide hydratase activity. During the last decade, dinitroaniline compound-based therapies against protozoan diseases are being developed. Therefore, it is important to investigate their potential off-target effects, including human CAs.

Significance of Nitric Oxide Level in Giardiasis.

BACKGROUND: Giardiasis is one of the most prevalent intestinal protozoa infections in humans. Nowadays, nitric oxide (NO) is known to be involved in the immune system against Giardia intestinalis. Therefore, the aim of the present study was to evaluate the level of NO in individuals with giardiasis in comparison to normal subjects. METHODS: This descriptive study was conducted among 49 Giadia positive and 39 age and gender matched healthy volunteers. Examination of stool samples was done by wet mount technique and formol-ether concentration method. Serum samples were obtained for laboratory examination. NO production was quantified by measuring nitrite, a stable end product of NO, using the Griess reaction based on ELISA method. By using the standard curve in Excel program, the concentration of NO2- in samples was obtained. Finally, all data were analyzed using SPSS version 17. RESULTS: Values obtained from NO assays were placed into 4 groups: ≤ 10 (decline), 10.01 - 15 (normal), 15.01 - 25 (increase), and more than 25 µM (sharp increase). The mean level of NO in patients with G. intestinalis was 32.19 ± 2.15 µM and in people without G. intestinalis was 17.1 ± 1.33 µM. Eight point two percent of patients with Giardiasis were in normal range, but 2%, 20.4%, and 69.4% were in decline, increase, and sharp increase ranges, respectively. In group 2 (without infection), 17.9% were in normal range, and 20.5%, 51.3%, and 10.3% were in decline, increase, and sharp increase ranges, respectively. There was a statistical difference in nitric oxide levels between positive and negative groups with a 95% confidence interval. (p-value = 0.001). CONCLUSIONS: In our study, the number of people who showed a sharp increase in NO levels was significantly higher in individuals with giardiasis as compared to the control group, and patients infected with giardiasis showed significant increase in NO levels. Therefore, we suggest that further studies are required to understand the exact function of NO in the immune system against giardiasis in humans. It will be important to offer a new therapeutic target for eliminating G. intestinalis.

Optimization and Comparison of Synthetic Procedures for a Group of Triazinyl-Substituted Benzene-Sulfonamide Conjugates with Amino Acids.

Sulfonamides incorporating 1,3,5-triazine moieties can selectively and potently inhibit carbonic anhydrase transmembrane isoforms IX, XII, and XIV over cytosolic isoforms I and II. In the present work, a highly effective synthetic procedure was proposed for this group of potent cancerostatic drugs and compared with previously used methods. The synthesis of triazinyl-substituted benzene-sulfonamide conjugates with amino acids can be easily carried out using sodium carbonate-based water solution as a synthetic medium instead of N,N-Diisopropylethylamine/Dimethylformamide. The benefits of this synthetic procedure include: (i) high selectivity of the creation of disubstituted conjugates; (ii) several times higher yield (≥95%) than that achieved previously; (iii) elimination of organic solvents by the use of an environmental friendly water medium (green chemistry); (iv) simple and fast isolation of the product. The synthesis and resulting products were evaluated using TLC, IR, NMR, and MS methods. The present work demonstrates a significant advantage in providing shortened routes to target structures.

Sulfonamide inhibition studies of the γ-carbonic anhydrase from the Antarctic bacterium Colwellia psychrerythraea.

The Antarctic bacterium Colwellia psychrerythraea encodes for a γ-class carbonic anhydrase (CA, EC 4.2.1.1), which was cloned, purified and characterized. The enzyme (CpsCAγ) has a moderate catalytic activity for the physiologic reaction of CO2 hydration to bicarbonate and protons, with a k(cat) 6.0×10(5) s(-1) and a k(cat)/K(m) of 4.7×10(6) M(-1) s(-1). A series of sulfonamides and a sulfamate were investigated as inhibitors of the new enzyme. The best inhibitor was metanilamide (K(I) of 83.5 nM) followed by indisulam, valdecoxib, celecoxib, sulthiame and hydrochlorothiazide (K(I)s ranging between 343 and 491 nM). Acetazolamide, methazolamide as well as other aromatic/heterocyclic derivatives showed inhibition constants between 502 and 7660 nM. The present study may shed some more light regarding the role that γ-CAs play in the life cycle of psychrophilic bacteria as the Antarctic one investigated here, by allowing the identification of inhibitors which may be useful as pharmacologic tools.

Discovery of 2-azetidinone and 1H-pyrrole-2,5-dione derivatives containing sulfonamide group at the side chain as potential cholesterol absorption inhibitors.

Cholesterol absorption inhibitor (CAI) targeting Niemann-Pick C1-like1 protein was developed for the treatment of hyperlipidaemia and only ezetimibe was approved so far. For developing novel CAIs, we synthesized sixteen 2-azetidinone derivatives and thirteen 1H-pyrrole-2,5-dione derivatives containing sulfonamide group at the side chain, and their inhibitory activity of cholesterol absorption was evaluated in Caco-2 cell line in vitro. Furthermore, top six compounds were measured by cytotoxicity and partition coefficient, and 2-azetidinone analogue 9e was selected for in vivo study. Finally, 9e considerably reduced total cholesterol, LDL-C, FFA and triglyceride in the serum and increased the rate of HDL-C to total cholesterol, suggesting it could regulate the lipid metabolism and act as a potent CAI.

Hypervalency in Organic Crystals: A Case Study of the Oxicam Sulfonamide Group.

The theoretical charge density of the active pharmaceutical ingredient piroxicam (PXM) was evaluated through density functional theory with a localized basis set. To understand the electronic nature of the sulfur atom within the sulfonamide group, a highly ubiquitous functional group in pharmaceutical molecules, a theoretical charge density study was performed on PXM within the framework of Bader theory. Focus is on developing a topological description of the sulfur atom and its bonds within the sulfonamide group. It was found that sulfur d-orbitals do not participate in bonding. Instead, the existence of a strongly polarized ("ionic") bonding structure is found through a combined topological and natural bonding orbital analysis. This finding is in stark contrast to long-held theories of the bonding structure of organic sulfonamide and has important implications for the parametrization of calculations using classical approaches.

Photodegradation of Oryzalin in aqueous isopropanol and acetonitrile.

The phototransformation of Oryzalin was studied under UV light (λmax ≥ 290 nm) and sunlight (λmax ≥ 250 nm) in aqueous isopropanol and acetonitrile solution in absence and presence of TiO2 as sensitizer. The rate of photodegradation of Oryzalin in different solvent system followed first-order kinetics, and calculated half-lives were found to be in the range of 23.52-53.75 h for UV light and 41.23-61.43 h for sunlight. From this study, total 12 photoproducts were identified and characterized on the basis of column chromatography and Q-Tof micromass spectral data. The plausible mechanism of phototransformation involved was hydrolysis, breaking of sulfonic bond, and loss of amino and sulfonic acid group.

Arabidopsis dynamin-related proteins, DRP2A and DRP2B, function coordinately in post-Golgi trafficking.

Dynamin-related proteins (DRPs) are large GTPases involved in a wide range of cellular membrane remodeling processes. In Arabidopsis thaliana, two paralogous land plant-specific type DRPs, DRP2A and DRP2B, are thought to participate in the regulation of post-Golgi trafficking. Here, we examined their molecular properties and functional relationships. qRT-PCR and GUS assays showed that DRP2A and DRP2B were expressed ubiquitously, although their expressions were strongest around root apical meristems and vascular bundles. Yeast two-hybrid, bi-molecular fluorescent complementation, and co-immunoprecipitation mass spectrometry analyses revealed that DRP2A and DRP2B interacted with each other. In observations with confocal laser scanning microscopy and variable incidence angle fluorescent microscopy, fluorescent fusions of DRP2A and DRP2B almost completely co-localized and were mainly localized to endocytic vesicle formation sites of the plasma membrane, clathrin-enriched trans-Golgi network and the cell plate in root epidermal cells. Treatments with wortmannin, an inhibitor of phosphatidylinositol 3-/4-kinases, latrunculin B, an inhibitor of actin polymerization, and oryzalin, an inhibitor of microtubule polymerization, increased the resident time of DRP2A and DRP2B on the plasma membrane. These results show that DRP2A and DRP2B function coordinately in multiple pathways of post-Golgi trafficking in phosphatidylinositol 3- or 4-kinase and cytoskeleton polymerization-dependent manners.

Development and Validation of an HPLC-UV Assay to Quantify Plasma Levels of Sulfametrol: A Preferential Antibiotic in Children.

BACKGROUND: Sulfonamides in combination with trimethoprim are frequently used antibiotics. They work synergistic. In infections with Pneumocystis jiroveci or Stenotrophomonas maltophilia, higher dosages are indicated than in other infections. Therapeutic drug monitoring (TDM) is warranted to assure the efficacy while limiting toxicity. Although trimethoprim in combination with sulfamethoxazole is the most common combination with established TDM target concentrations, the intravenous formulation is not suited for children because of its additives ethanol and propylene glycol to increase solubility. An alternative can be sulfametrol in combination with trimethoprim. When sulfametrol was introduced in the hospital, there was a need for a TDM method for sulfametrol. METHODS: A High Pressure Liquid Chromatography-Ultraviolet (HPLC-UV) detection method for sulfametrol determination in plasma was developed and validated according to the International Conference on Harmonization guidelines. Linearity, limit of detection, lower limit of quantification, recovery, process efficiency, selectivity, within-run precision, between-run precision, and sample stability were tested. RESULTS: All tested parameters met the required criteria. For linearity, r was 0.9948, lower limit of quantification was 10 mg/L, and limit of detection was 6 mg/L. Recovery was 100.4% and process efficiency 94.4%. Selectivity was met with no interfering peaks at the retention time of 4.2 minutes. Between-run precision and within-run precision were evaluated by replicating quality control levels, resulting in a within-run relative average standard deviation of 0.8% and a between-run relative standard deviation of 2.3%. Recovery of the samples after storing 8 days was 101.9% and recovery of already tested vials was 98.8% after 48 hours. CONCLUSIONS: In conclusion, an HPLC-UV method for sulfametrol determination in human plasma was developed and validated. The method is fast, accurate, reproducible, and has a short analysis time. It is now being used in routine TDM in our clinic.

The ß-carbonic anhydrase from the malaria mosquito Anopheles gambiae is highly inhibited by sulfonamides.

A ß-carbonic anhydrase (CA, EC 4.2.1.1) was cloned, purified and characterized from Anopheles gambiae, the mosquito species mainly involved in the transmission of malaria. The new enzyme, AgaCA, showed a significant catalytic activity for the physiologic reaction, CO2 hydration to bicarbonate and protons, with a kcat of 7.2×10(5)s(-1) and kcat/Km of 5.6×10(7)M(-1)s(-1), being thus similar to parasite ß-CAs which were discovered earlier as drug targets for antifungal or anti-protozoan agents. An inhibition study of AgaCA with a panel of aromatic, aliphatic and heterocyclic sulfonamides allowed us to identify several low nanomolar inhibitors of the enzyme. Benzolamide and aminobenzolamide showed inhibition constants of 6.8-9.8nM, whereas a structurally related aromatic derivative, 4-(2-hydroxymethyl-4-nitrophenyl-sulfonamidoethyl)-benzenesulfonamide was the strongest inhibitor with a KI of 6.1nM. As ß-CAs are not present in mammals, including humans, finding effective and selective A. gambiae CA inhibitors may lead to alternative procedures for controlling malaria by impairing the growth of its transmission vector, the mosquito.

Sulfonamide inhibition studies of the γ-carbonic anhydrase from the Antarctic cyanobacterium Nostoc commune.

A carbonic anhydrase (CA, EC 4.2.1.1) belonging to the γ-class has been cloned, purified and characterized from the Antarctic cyanobacterium Nostoc commune. The enzyme showed a good catalytic activity for the physiologic reaction (hydration of carbon dioxide to bicarbonate and a proton) with the following kinetic parameters, kcat of 9.5×10(5)s(-1) and kcat/KM of 8.3×10(7)M(-1)s(-1), being the γ-CA with the highest catalytic activity described so far. A range of aromatic/heterocyclic sulfonamides and one sulfamate were investigated as inhibitors of the new enzyme, denominated here NcoCA. The best NcoCA inhibitors were some sulfonylated sulfanilamide derivatives possessing elongated molecules, aminobenzolamide, acetazolamide, benzolamide, dorzolamide, brinzolamide and topiramate, which showed inhibition constants in the range of 40.3-92.3nM. As 1,5-bisphosphate carboxylase/oxygenase (RubisCO) and γ-CAs are closely associated in carboxysomes of cyanobacteria for enhancing the affinity of RubisCO for CO2 and the efficiency of photosynthesis, investigation of this new enzyme and its affinity for modulators of its activity may bring new insights in these crucial processes.