Enzyme Carbonic Anhydrase Research Articles

Thin-blooded icefish relocate carbonic anhydrase to gill

Few animals can justifiably be called ‘thin blooded’, but Antarctic icefish genuinely are. They lack the brightly pigmented red blood cells that usually carry oxygen around the body, although the blood is still capable of transporting oxygen to their tissues thanks to the high solubility of the gas in the frigid Antarctic waters. But the fish face another problem. In most bony fish, waste carbon dioxide is carried in the blood to the gills in the form of bicarbonate, where it is converted back into carbon dioxide in red blood cells by an enzyme known as carbonic anhydrase, before it is exhaled. ‘However this strategy is impossible in icefishes, which have lost red blood cells’, says Till Harter from the University of British Columbia, Canada. While there is some evidence that the essential bicarbonate converting protein is harboured somewhere in the gills, the precise location was not clear. Reasoning that it might be might be situated on the inner surface of gill blood vessels, Harter, Colin Brauner and their international team of collaborators began searching for the elusive enzyme in the gills of Champsocephalus gunnari icefish.Although Harter was unable to visit Antarctica himself, he was fortunate that Kristin O'Brien from University of Alaska Fairbanks, USA, and Lisa Crockett from Ohio University, USA, sent C. gunnari that they had caught during the 2015 Antarctic field season. After the fish arrived, he cautiously isolated the outer membrane from the cells lining the inside of the gill blood vessels before bathing it in water saturated with CO2 and measuring how the pH changed – in the hope that any carbonic anhydrase present on the membrane surface may convert the gas into bicarbonate. The pH decreased rapidly, confirming that the enzyme is located on blood vessel cell membranes. And when Jonathan Wilson stained the cell membranes with a series of specialised dyes that could only bind to molecules of carbonic anhydrase, he found one form of the enzyme (carbonic anhydrase 4) attached to the membranes lining the inner surface of the gill blood vessels. To confirm the presence of the enzyme, Harter and David Metzger then collected RNA from the fish's gills, eventually identifying an mRNA molecule that could be translated to produce the carbonic anhydrase 4 enzyme. However, when the team searched for carbonic anhydrase proteins in the gills of a close relative, Notothenia rossii, which has retained its red blood cells despite sharing C. gunnari’s icy waters, they found none.So, it seems that icefish have relocated carbonic anhydrase to their gills to overcome the difficulties of carbon dioxide disposal after trading in their red blood cells. But they suspect that red-blooded fish are unlikely to follow their apparently ‘bloodless’ cousin's convenient example, as the enzyme could drastically disturb the delicate balance that allows their red blood cells to keep hold of their oxygen cargo when exercising hard.

In vitro cytotoxic and in vivo antitumoral activities of some aminomethyl derivatives of 2,4-dihydro-3H-1,2,4-triazole-3-thiones-Evaluation of their acetylcholinesterase and carbonic anhydrase enzymes inhibition profiles.

The 1,2,4-triazole and its derivatives were reported to exhibit various pharmacological activities such as antimicrobial, analgesic, anti-inflammatory, antitumoural, cytotoxic, and antioxidant properties. In this study, a series of triazole compounds (M1-M10) were evaluated for some biological activities. In vitro qualifications of these compounds on acetylcholinesterase (AChE) and human carbonic anhydrase enzyme activities were performed. Also, their antitumoral activities in human colon cancer (HT29) cell line cultures were examined. In addition, colon cancer experimentation was induced in rats by an in vivo method, and the in vivo anticancer effects of triazole derivatives were investigated. Also, the effects of these derivatives in levels of antioxidant vitamin A, vitamin E, and MDA were studied in rat liver and blood samples. Most of the compounds were found to exhibit significant antioxidant and antitumoral activities. All the compounds had cytotoxic activities on HT29 cell lines with their IC50 values lower than 10 µM concentrations. The low IC 50 values of the compounds are M1 (3.88 µM), M2 (2.18 µM), M3 (4.2 µM), M4 (2.58 µM), M5 (2.88 µM), M6 (2.37 µM), M7 (3.49 µM), M8 (4.01 µM), M9 (8.90 µM), and M10 (3.12 µM).

4-Substituted benzenesulfonamides featuring cyclic imides moieties exhibit potent and isoform-selective carbonic anhydrase II/IX inhibition

The synthesis, characterization and biological evaluation of series of cyclic imides incorporating the 4-sulfamoylbenzamide scaffold (16–29) is disclosed. The compounds were designed by application of the “tail approach” to the aromatic sulfonamide scaffold and prepared by reacting the proper acid anhydride with 4-(hydrazinecarbonyl)benzenesulfonamide (15). Phtalimides and cyclic imides are biologically privileged scaffolds, endowed with versatile biological activity, such as an anti-proliferative action. The compounds were investigated for the inhibition of four human (h) isoforms of zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1), and more specifically against the cytosolic hCA I and II and the transmembrane hCA IV and IX. Most screened sulfonamides exhibited great potency in inhibiting CA isoforms II, widely involved in glaucoma and other pathologies (KIs in the range of 0.7–62.3 nM), and IX, that is a validated anti-tumor target (KIs in the range of 3.0–50.9 nM), whereas interesting hydrophilicity-dependent inhibitory profiles were measured against isoform CA IV (KIs in the range of 3.9–428.6 nM). In silico studies were carried out to assess the binding mode of selected derivatives to hCA II, IV and IX.

Urease inhibitory potential of extracts and active phytochemicals of Hypochaeris radicata (Asteraceae)

Urease inhibition potential of compound (1), guaiane-type sesquiterpene (2), confertin (3) and scopoletin (4) was carried out with high throughout mechanism-based assay. These compounds were isolated from Hypochaeris radicata L., an Asteraceae family member. The pure compounds were screened for their urease and carbonic anhydrase inhibitory activities. The ethyl acetate fractions were subjected to column chromatography, which resulted in the isolation and purification of four compounds (1–4). On evaluation, compounds (1–4) exhibited selective activity against urease enzyme with an IC50 value of 180.11 ± 2.00, 27.18 ± 0.80, 24.12 ± 0.2 and 30.12 ± 1.10 µM respectively. The compounds (1–4) were found to be inactive against carbonic anhydrase enzyme. Thiourea was used as standard inhibitor (21 ± 0.14 µM) of urease enzyme.

Carbonic Anhydrase Enzyme-MOFs Composite with a Superior Catalytic Performance to Promote CO2 Absorption into Tertiary Amine Solution.

Carbonic anhydrase (CA) enzyme-based absorption technology for CO2 capture has been intensively investigated. The main issue related to this novel technology is the activity and stability of the CA enzyme under the typical flue gas conditions. To address this issue, CA enzymes were embedded into zeolitic imidazolate framework (ZIF-L) nanoparticles to synthesize a novel CA/ZIF-L-1 composite. The composite exhibited a superior apparent catalytic activity (1.5 times higher) for CO2 absorption compared with their free counterparts, which was due to the synergistic enhancement of CO2 adsorption by support ZIF-L and enzymatic catalysis. The analyses of Fourier transform infrared spectroscopy and circular dichroism revealed that the CA enzyme's secondary structure was not significantly varied during the CA/ZIF-L-1 preparation, resulting in a high enzyme activity retention. Moreover, the CA/ZIF-L-1 possessed a high thermal stability and reusability due to the structural rigidity and confinement of ZIF-L scaffolds. Compared with the free enzyme, its thermal stability was improved by approximately 100% at 40 °C. After six cycles of reuse, CA/ZIF-L-1 still retained a relative activity of 134%. Therefore, the CA/ZIF-L-1 can be a good candidate to promote the CO2 capture in industrial application.

Modelling of Enzymatic Reactive CO 2 Absorption

Post-combustion CO2 capture strategy asks for novel effective processes avoiding the use of polluting solvents and oriented towards CO2 utilization. Recent research efforts are focused on the development of CO2 absorption processes promoted by the activity of the enzyme carbonic anhydrase (EC - 4.2.1.1) (Leimbrik et al., 2017; Russo et al., 2013). This ubiquitous enzyme is able to catalyse the CO2 hydration reaction and can be used to enhance CO2 absorption rate into aqueous alkaline solvents such as carbonate solutions. The adoption of the biomimetic strategy for post-combustion CO2 capture is based on the use of environmental friendly solvents. Recent studies on the development of carbonic anhydrase biocatalysts for CO2 capture through enzymatic reactive absorption focused on different enzyme immobilization techniques. Moreover, theoretical studies showed the potential use of immobilized enzymes in typical gas-liquid contactors. The present contribution concerns the rational design of absorption columns through the use of kinetic parameters assessed for carbonic anhydrase immobilized on fine particles. The kinetics of CA immobilized on magnetic nanoparticles have been previously characterized under conditions relevant for the industrial application (K2CO3 solutions at 25-40°C and at different carbonate conversion degrees) (Peirce et al., 2017; Peirce, 2017). The model simulations provided information on the performances of the technical grade CA and of the biocatalyst made with nanoparticles (NPs) coated with covalently immobilized CA. The results showed that effective intensification of the capture process can be achieved using the fine slurry biocatalyst.

1,2,4-Trisubstituted imidazolinones with dual carbonic anhydrase and p38 mitogen-activated protein kinase inhibitory activity

Various 1,2,4 trisubstituted imidazolin-5-one derivatives were synthesized and evaluated for their inhibitory activity against p38 mitogen-activated protein kinase (p38MAPK) and carbonic anhydrase (CA) enzymes aiming to explore potential dual inhibitors. Results revealed that compounds 3c, 3g, 3h, 4a, 6c and 6d were the most effective derivatives against p38αMAPK (IC50 = 0.14, 0.14, 0.056, 0.14, 0.13 and 0.14 μM, respectively) compared to sorafenib (IC50 = 1.58 μM) as standard drug. On the other hand, compound 4a revealed the best inhibitory activity against all the tested carbonic anhydrase isoforms CA I, II, IV and IX with Ki values of 95.0, 0.83, 6.90 and 12.4 nM, respectively compared to acetazolamide with Ki values 250, 12.1, 74 and 12.8 nM, respectively. Therefore, compound 4a can be considered as a potent dual p38αMAPK/CA inhibitor.

Novel sulfamate derivatives of menthol: Synthesis, characterization, and cholinesterases and carbonic anhydrase enzymes inhibition properties.

Sulfamates have a large spectrum of biological activities including enzyme inhibition. Eight sulfamates derived from menthol (2a-h) were synthesized. Also, in the other section of this study, novel sulfamate derivatives of menthol were tested against some metabolic enzymes including acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and carbonic anhydrase I and II enzymes (hCAs I and II). The newly synthesized novel menthol sulfamate and menthol carbonyl sulfamate derivatives showed Ki values in the range of 34.37 ± 8.17 to 53.40 ± 10.61 nM against hCA I, 12.91 ± 4.57 to 38.67 ± 6.22 nM against hCA II, 111.17 ± 52.36 to 522.86 ± 120.08 nM against AChE, and 50.01 ± 11.73 to 109.63 ± 50.08 nM against BChE. As a result, the novel menthol sulfamate and menthol carbonyl sulfamate derivatives can be promising Alzheimer's disease drug candidates and novel hCA I and hCA II enzymes inhibitors.

Arctic Coralline Algae Elevate Surface pH and Carbonate in the Dark.

Red coralline algae are projected to be sensitive to ocean acidification, particularly in polar oceans. As important ecosystem engineers, their potential sensitivity has broad implications, and understanding their carbon acquisition mechanisms is necessary for making reliable predictions. Therefore, we investigated the localized carbonate chemistry at the surface of Arctic coralline algae using microsensors. We report for the first time carbonate ion concentration and pH measurements ([CO32-]) at and above the algal surface in the microenvironment. We show that surface pH and [CO32-] are higher than the bulk seawater in the light, and even after hours of darkness. We further show that three species of Arctic coralline algae have efficient carbon concentrating mechanisms including direct bicarbonate uptake and indirect bicarbonate use via a carbonic anhydrase enzyme. Our results suggest that Arctic corallines have strong biological control over their surface chemistry, where active calcification occurs, and that net dissolution in the dark does not occur. We suggest that the elevated pH and [CO32-] in the dark could be explained by a high rate of light independent carbon fixation that reduces respiratory CO2 release. This mechanism could provide a potential adaptation to ocean acidification in Arctic coralline algae, which has important implications for future Arctic marine ecosystems.

Some pyrazoles derivatives: Potent carbonic anhydrase, α-glycosidase, and cholinesterase enzymes inhibitors.

A series of substituteed pyrazol-4-yl-diazene derivatives were found to be effective inhibitors against α-glycosidase, cytosolic carbonic anhydrase I and II isoforms (hCA I and II), butyrylcholinesterase (BChE), and acetylcholinesterase (AChE) with Ki values in the range of 33.72 ± 7.93 to 90.56 ± 27.52 nM for α-glycosidase, 1.06 ± 0.16 to 9.83 ± 0.74 nM for hCA I, 0.68 ± 0.12 to 7.16 ± 1.14 nM for hCA II, 44.66 ± 10.06 to 78.34 ± 17.83 nM for AChE, and 50.36 ± 13.88 to 88.36 ± 20.03 nM for BChE, respectively. Recently, inhibition of these metabolic enzymes has been considered as a promising factor for pharmacologic intervention in a diversity of disturbances, such as diabetes, glaucoma, obesity, epilepsy, cancer, and neurodegenerative diseases.

Mechanism of boron incorporation into calcites and associated isotope fractionation in a steady-state carbonate-seawater system

An investigation on the interface reactions and boron isotope fractionation in a steady-state carbonate-seawater system was performed to better understand boron incorporation into CaCO3 in a natural environment. In seawater, inorganic carbonate crystals did not precipitate even when the solution reached saturation and the presence of carbonic anhydrase enzyme promotes the process, indicating the precipitation kinetics of inorganic carbonates from natural seawater is fairly slow. Both theoretical and experimental evidence proved that boron incorporation into calcite might be defined as an adsorption-precipitation process rather than a substitution of CO32− by HBO32− in the crystal lattice, where the charged B(OH)4- ions adsorb preferentially over H3BO3 onto positively charged calcite crystal surfaces and finally co-precipitate into occlusions or inclusions after new layers of calcites formed. The Langmuir isotherm well describes the adsorption process, yielding a maximum adsorption capacity [B]solid-max of 0.33 ± 0.04 mg⋅g−1 and an equilibrium constant K of 0.0053 ± 0.0003. Langmuir kinetics also describes previous studies with [B]solid-max of 71.4–418 μg⋅g−1 for calcite and aragonite, covering the variation of boron contents in a variety of biogenic carbonates. The boron isotope fractionations in ulexite-seawater and calcite-seawater systems are distinct. In the former one the fractionation factor (αulexite-seawater = 0.995 ± 0.001) suggests that both trigonal and tetrahedral species of boron enter into ulexite crystals via rapid precipitation, and in the latter one (α4-3 = 0.9736 ± 0.004) confirms that only the charged B(OH)4- species interacts with the crystal surface in calcite.

The effect of sodium nitrite infusion on renal function, brachial and central blood pressure during enzyme inhibition by allopurinol, enalapril or acetazolamide in healthy subjects: a randomized, double-blinded, placebo-controlled, crossover study

BackgroundSodium nitrite (NaNO2) causes vasodilation, presumably by enzymatic conversion to nitric oxide (NO). Several enzymes with nitrite reducing capabilities have been discovered in vitro, but their relative importance in vivo has not been investigated. We aimed to examine the effects of NaNO2 on blood pressure, fractional sodium excretion (FENa), free water clearance (CH2O) and GFR, after pre-inhibition of xanthine oxidase, carbonic anhydrase, and angiotensin-converting enzyme. The latter as an approach to upregulate endothelial NO synthase activity.MethodsIn a double-blinded, placebo-controlled, crossover study, 16 healthy subjects were treated, in a randomized order, with placebo, allopurinol 150 mg twice daily (TD), enalapril 5 mg TD, or acetazolamide 250 mg TD. After 4 days of treatment and standardized diet, the subjects were examined at our lab. During intravenous infusion of 240 μg NaNO2/kg/hour for 2 h, we measured changes in brachial and central blood pressure (BP), plasma cyclic guanosine monophosphate (P-cGMP), plasma and urine osmolality, GFR by 51Cr-EDTA clearance, FENa and urinary excretion rate of cGMP (U-cGMP) and nitrite and nitrate (U-NOx). Subjects were supine and orally water-loaded throughout the examination day.ResultsIrrespective of pretreatment, we observed an increase in FENa, heart rate, U-NOx, and a decrease in CH2O and brachial systolic BP during NaNO2 infusion. P-cGMP and U-cGMP did not change during infusion. We observed a consistent trend towards a reduction in central systolic BP, which was only significant after allopurinol.ConclusionThis study showed a robust BP lowering, natriuretic and anti-aquaretic effect of intravenous NaNO2 regardless of preceding enzyme inhibition. None of the three enzyme inhibitors used convincingly modified the pharmacological effects of NaNO2. The steady cGMP indicates little or no conversion of nitrite to NO. Thus the effect of NaNO2 may not be mediated by NO generation.Trial registrationEU Clinical Trials Register, 2013-003404-39. Registered December 3 2013.

Carbonic anhydrase regulation of plankton community structure in estuarine systems

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 82:73-85 (2018) - DOI: https://doi.org/10.3354/ame01879 Carbonic anhydrase regulation of plankton community structure in estuarine systems Eilea R. Knotts1,*, James L. Pinckney2 1Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208, USA 2Baruch Institute for Marine and Coastal Sciences, School of Earth, Ocean and Environment, University of South Carolina, Columbia, South Carolina 29208, USA *Corresponding author: eilea.knotts@gmail.com ABSTRACT: Carbon concentrating mechanisms (CCMs) are used by phytoplankton to concentrate dissolved inorganic carbon within their cells for use in photosynthesis. However, CCMs which involve carbonic anhydrase (CA) may become redundant in the future due to increasing surface water dissolved CO2 (CO2(aq)) concentrations. Most of our knowledge of the CA enzyme is based on single-species phytoplankton cultures or oligotrophic water samples. Few studies have examined the consequences of CA activity on competitive interactions in estuarine phytoplankton communities or measured the long-term effects on community composition. Using bioassays of natural phytoplankton communities, we explored 2 different estuarine systems and determined how community composition was altered when the CA enzyme was removed. Using the CA inhibitor ethoxyzolamide (EZ), our results demonstrate that communities are altered when the inhibitor is present and CA activity is suppressed. Diatoms were the dominant taxonomic group in all samples following a 3 d exposure of the community to EZ. However, our findings suggest that diatom growth was both stimulated and inhibited, depending on the salinity of the location where samples were collected. Furthermore, microscopy of the high salinity phytoplankton community indicated that centric diatom genera (e.g. Skeletonema, Rhizosolenia) were severely reduced in treatments that removed the competitive advantage of CA, while pennate diatom genera (e.g. Asterionellopsis, Cylindrotheca) dominated these same treatments. These shifts in community structure suggest that phytoplankton composition is affected by carbon acquisition using CA, and some diatom genera may depend on the competitive advantage of this CCM to maintain high abundances in estuarine environments. KEY WORDS: Carbon acquisition · Carbon concentrating mechanisms · Community structure · Diatoms · Estuary · Phytoplankton Full text in pdf format PreviousNextCite this article as: Knotts ER, Pinckney JL (2018) Carbonic anhydrase regulation of plankton community structure in estuarine systems. Aquat Microb Ecol 82:73-85. https://doi.org/10.3354/ame01879 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 82, No. 1. Online publication date: September 20, 2018 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2018 Inter-Research.

Soil exchange rates of COS and CO18O differ with the diversity of microbial communities and their carbonic anhydrase enzymes

Differentiating the contributions of photosynthesis and respiration to the global carbon cycle is critical for improving predictive climate models. Carbonic anhydrase (CA) activity in leaves is responsible for the largest biosphere-atmosphere trace gas fluxes of carbonyl sulfide (COS) and the oxygen-18 isotopologue of carbon dioxide (CO18O) that both reflect gross photosynthetic rates. However, CA activity also occurs in soils and will be a source of uncertainty in the use of COS and CO18O as carbon cycle tracers until process-based constraints are improved. In this study, we measured COS and CO18O exchange rates and estimated the corresponding CA activity in soils from a range of biomes and land use types. Soil CA activity was not uniform for COS and CO2, and patterns of divergence were related to microbial community composition and CA gene expression patterns. In some cases, the same microbial taxa and CA classes catalyzed both COS and CO2 reactions in soil, but in other cases the specificity towards the two substrates differed markedly. CA activity for COS was related to fungal taxa and β-D-CA expression, whereas CA activity for CO2 was related to algal and bacterial taxa and α-CA expression. This study integrates gas exchange measurements, enzyme activity models, and characterization of soil taxonomic and genetic diversity to build connections between CA activity and the soil microbiome. Importantly, our results identify kinetic parameters to represent soil CA activity during application of COS and CO18O as carbon cycle tracers.

Inhibition of smoothened in breast cancer cells reduces CAXII expression and cell migration.

Breast cancer (BC) relapse and metastasis are the leading cause of death and, together with drug resistance, keep mortality still high. The Hedgehog (Hh) pathway is expressed during embryogenesis, organogenesis and in adult tissue homeostasis and its aberrant activation is often associated with cancer. Carbonic anhydrase (CA) enzymes are important during development; they play a key role in controlling several cellular mechanisms, such as pH regulation, survival, and migration, and they are aberrantly expressed in cancer. The goal of this study was to investigate the interplay between the Hh pathway and CAXII in terms of BC cell migration. We here demonstrated that smoothened (SMO) silencing resulted in a reduction of CAXII expression at mRNA and protein level. This led to a decrease in cell migration, which was restored when cells were treated with an SMO agonist, Sag dihydrochloride (SAG), but not when cells were cotreated with SAG and the CAs inhibitor Acetazolamide. This suggested that the ability of SAG to promote cell migration was impaired when CAXII was inhibited. The reduction was also confirmed within hypoxic and inflammatory microenvironment, typical of BC, indicating a key role of the Hh pathway in controlling CAXII expression. Our results may contribute to further understand the physiology of BC cells and indicate that the Hh pathway controls BC cell migration and cell invasion also through CAXII, with important implications in identifying novel therapeutic targets.

Synthesis, characterization, crystal structures, theoretical calculations and biological evaluations of novel substituted tacrine derivatives as cholinesterase and carbonic anhydrase enzymes inhibitors

The six and seven hydrocycle membered disilylanilino acridine (tacrine) analogues (9–11) were synthesized by one-pot procedures. The structures of novel silyl tacrine derivatives were characterized by NMR spectroscopy, elemental analysis and XRD investigations. The silyl substituted novel tacrine derivatives (9–11) were investigated as cholinesterase inhibitors and defined the relative role of AChE (Acetylcholinesterase) versus BChE (Butyrylcholinesterase) inhibition. Novel substituted tacrine derivatives are known as important inhibitors of Carbonic anhydrase (CA) isoenzymes I, and II (hCA I and II), therefore, the synthesized compounds (9–11) were investigated for inhibitory effects on the both CA isoenzymes. Additionally, we evaluated four different enzymes, which were inhibited in the very low nanomolar (nM) range by these compounds. According to the present studies, for AChE, BChE, hCA I and II, the ranges of results are recorded as 30.26 ± 6.71–117.54 ± 42.22 nM, 22.45 ± 5.81–77.41 ± 4.02 nM, 57.28 ± 22.16–213.41 ± 82.75 nM and 46.95 ± 11.32–274.94 ± 62.15 nM, respectively.

Anellotech move 100% bio-based bottle technology towards commercialization

Carbon dioxide absorption into carbonate solutions promoted by the enzyme carbonic anhydrase (CA, E.C. 4.2.1.1) has been proposed as potential technology for CO2 capture. The use of solid CA-based biocatalysts allows the enzyme recovery and reuse under continuous operating conditions typical of industrial applications. The present study regards the development and the kinetic characterization of a solid CA-based biocatalyst to be used in CO2 capture processes based on reactive absorption. A technical grade thermostable CA was immobilized by covalent bonding on aminated paramagnetic Fe3O4 nanoparticles via carbodiimide activation of the enzyme. The effective covalent binding of the enzyme on the support was verified in the alkaline carbonate solution used as solvent for CO2 absorption tests. The kinetics of the biocatalyst were assessed by means of CO2 absorption tests in a stirred cell reactor. The liquid solvents used in the CO2 absorption tests were 0.5 M Na2CO3/NaHCO3 buffer (pH 9.6) at 298 and 313° K and 10% wt/wt K2CO3 solutions at different carbonate conversion degrees (0–40%). The Danckwerts’ theory for gas-liquid reactive absorption was applied to assess the intrinsic second order kinetic constant kcat/KM for the CO2 hydration reaction catalyzed by the immobilized CA. Results pointed out that kcat/KM ranged between 102 and 103 m3∙kg−1∙s−1 and that it increased with the temperature and with the decrease of carbonate conversion degree.

Schiff bases and their amines: Synthesis and discovery of carbonic anhydrase and acetylcholinesterase enzymes inhibitors.

Three series of symmetrical Schiff bases were synthesized from 1,2-diaminoethane, 1,3-diaminopropane and 1,4-diaminobutane and substituted benzaldehydes, and reduced by sodium borohydride to the corresponding benzylic diamines 4-6. All of the compounds obtained were characterized using elemental analysis, FT-IR, 1 H NMR, and 13 C NMR spectroscopy. The enzyme inhibitory properties of these compounds were tested and the influence of the alkane chain length and the substituents on the phenyl group on the enzyme inhibition activity were examined. The novel Schiff bases and their amine derivatives (1a-d, 2a-d, 3b-d, 4a-c, 5a-c, 6a, 6c, 6d) were effective inhibitors of the cytosolic carbonic anhydrase I and II isoforms (hCA I and II), and acetylcholinesterase (AChE) with Ki values in the range of 159.43 ± 30.03 to 563.73 ± 115.30 nM for hCA I, 104.88 ± 18.44 to 524.32 ± 95.03 nM for hCA II, and 3.95 ± 0.74 to 30.83 ± 6.81 nM for AChE.

Intracellular carbonic anhydrase from Citrobacter freundii and its role in bio-sequestration

The aim of this work was to study the CO2 bio-sequestration application of indigenous Citrobacter species and its carbonic anhydrase (CA). Intracellular CA was purified from Citrobacter freundii (CF; accession no: MH283871) isolated from limestone rock site in Kumaun region of Indian Himalaya studied for the sequestration of carbon dioxide and the formation of calcite. CF showed maximum CA enzyme activity at 11.3 EU/ml at pH 7.0 and 37 °C. Hydration of CO2 into carbonate was characterized by calcite phase of calcium carbonate using absorption spectroscopy and imaging technique. Purified CA showed a significantly high CO2 sequestration capacity of 230 mg CaCO3/mg of purified as compared to crude enzyme (50 mg CaCO3/ml of enzyme).

Characterization and inhibition effects of some metal ions on carbonic anhydrase enzyme from Kangal Akkaraman sheep.

In this work, the carbonic anhydrase (CA) enzyme was purified from Kangal Akkaraman sheep in Sivas, Turkey with specific activity value of 6681.57EU/mg and yield of 14.90% with using affinity column chromatography. For designating the subunit molecular mass and enzyme purity, sodium dodecyl sulfate polyacrylamide gel electrophoresis method was used and single band for this procedure was obtained. The molecular mass of CA enzyme was found as 28.89kDa. In this study, the optimum temperature and optimum pH were obtained from 30 and 7.5. Vmax and Km values for p-nitrophenylacetate substrate of the CA were determined from Lineweaver-Burk graphs. Additionally, the inhibitory results of diverse heavy metal ions (Hg+ , Fe2+ , Pb2+ , Co2+ , Ag+ , and Cu2+ ) on sheep were studied. Indeed, CA enzyme activities of Kangal sheep were investigated with using esterase procedure under in vitro conditions. The heavy metal concentrations inhibiting 50% of enzyme activity (IC50 ) and Ki values were obtained.