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Acetazolamide-insensitive carbonic anhydrase activities in liver and tonic skeletal muscle of adult male rats with streptozotocin-induced diabetes mellitus.

ABSTRACT: One of the four discrete isoenzymes of carbonic anhydrase hitherto characterized, CA III, has the lowest turnover rate and the greatest resistance to inhibition by sulphonamides. Streptozotocin-induced diabetes mellitus resulted in a reduction in acetazolamide-resistant activity of carbonic anhydrase in the liver, but not in tonic skeletal muscle, of adult male rats. The hepatic activity declined with apparent first-order kinetics [calculated rate constant (k) 0.089 day-1] to a minimum of approx. 6% of control values; the reduction in activity was moderated by administration of insulin.

SUBMITTER: Moynihan JB

PROVIDER: S-EPMC1149739 | biostudies-other | 1990 Dec

REPOSITORIES: biostudies-other

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Neutron diffraction of acetazolamide-bound human carbonic anhydrase II reveals atomic details of drug binding.

Project description:Carbonic anhydrases (CAs) catalyze the hydration of CO(2) forming HCO(3)(-) and a proton, an important reaction for many physiological processes including respiration, fluid secretion, and pH regulation. As such, CA isoforms are prominent clinical targets for treating various diseases. The clinically used acetazolamide (AZM) is a sulfonamide that binds with high affinity to human CA isoform II (HCA II). There are several X-ray structures available of AZM bound to various CA isoforms, but these complexes do not show the charged state of AZM or the hydrogen atom positions of the protein and solvent. Neutron diffraction is a useful technique for directly observing H atoms and the mapping of H-bonding networks that can greatly contribute to rational drug design. To this end, the neutron structure of H/D exchanged HCA II crystals in complex with AZM was determined. The structure reveals the molecular details of AZM binding and the charged state of the bound drug. This represents the first determined neutron structure of a clinically used drug bound to its target.

| S-EPMC3524527 | biostudies-literature

Carbonic anhydrase C in white-skeletal-muscle tissue.

Project description:We investigated the activity of carbonic anhydrase in blood-free perfused white skeletal muscles of the rabbit. Carbonic anhydrase activities were measured in supernatants and in Triton extracts of the particulate fractions of white-skeletal-muscle homogenate by using a rapid-reaction stopped-flow apparatus equipped with a pH electrode. An average carbonic anhydrase concentration of about 0.5 microM was determined for white skeletal muscle. This concentration is about 1% of that inside the erythrocyte. Some 85% of the muscle enzyme was found in the homogenate supernatant, and only 15% appeared to be associated with membranes and organelles. White-skeletal-muscle carbonic anhydrase was characterized in terms of its Michaelis constant and catalytic-centre activity (turnover number) for CO2 and its inhibition constant towards ethoxzolamide. These properties were identical with those of the rabbit erythrocyte carbonic anhydrase C, suggesting that a type-C enzyme is present in white skeletal muscle. Affinity chromatography of muscle supernatant and of lysed erythrocytes showed that, whereas rabbit erythrocytes contain about equal amounts of carbonic anhydrase isoenzymes B and C, the B isoenzyme is practically absent from white skeletal muscle. Similarly, ethoxzolamide-inhibition curves suggested that white skeletal muscle contains no carbonic anhydrase A. It is concluded that white skeletal muscle contains essentially one carbonic anhydrase isoenzyme, the C form, most of which is probably of cytosolic origin.

| S-EPMC1158521 | biostudies-other

Cloning, purification and preliminary crystallographic analysis of the complex of Helicobacter pylori ?-carbonic anhydrase with acetazolamide.

Project description:Helicobacter pylori infection of the stomach can lead to severe gastroduodenal diseases such as gastritis, peptic ulcers and gastric cancers. Periplasmic H. pylori ?-carbonic anhydrase (Hp?CA) is essential for the acclimatization of the bacterium to the acidity of the stomach. Through the action of urease and carbonic anhydrases, the H. pylori periplasmic pH is maintained at around 6 in an environment with a pH as low as 2, which in turn facilitates the maintenance of a cytoplasmic pH close to neutral, allowing growth in the gastric niche. Crystals of Hp?CA in complex with the inhibitor acetazolamide have been grown by the hanging-drop vapour-diffusion method using polyethylene glycol as a precipitating agent. The crystals have the symmetry of space group P2(1)2(1)2(1), with unit-cell parameters a = 37.0, b = 82.4, c = 150.8?Å. An X-ray diffraction data set was collected from a single crystal to 1.7?Å resolution. Calculation of the self-rotation function using this data and molecular replacement showed that the asymmetric unit contains an Hp?CA dimer.

| S-EPMC3818046 | biostudies-literature

Structural studies of ?-carbonic anhydrase from the green alga Coccomyxa: inhibitor complexes with anions and acetazolamide.

Project description:The ?-class carbonic anhydrases (?-CAs) are widely distributed among lower eukaryotes, prokaryotes, archaea, and plants. Like all CAs, the ?-enzymes catalyze an important physiological reaction, namely the interconversion between carbon dioxide and bicarbonate. In plants the enzyme plays an important role in carbon fixation and metabolism. To further explore the structure-function relationship of ?-CA, we have determined the crystal structures of the photoautotroph unicellular green alga Coccomyxa ?-CA in complex with five different inhibitors: acetazolamide, thiocyanate, azide, iodide, and phosphate ions. The tetrameric Coccomyxa ?-CA structure is similar to other ?-CAs but it has a 15 amino acid extension in the C-terminal end, which stabilizes the tetramer by strengthening the interface. Four of the five inhibitors bind in a manner similar to what is found in complexes with ?-type CAs. Iodide ions, however, make contact to the zinc ion via a zinc-bound water molecule or hydroxide ion--a type of binding mode not previously observed in any CA. Binding of inhibitors to Coccomyxa ?-CA is mediated by side-chain movements of the conserved residue Tyr-88, extending the width of the active site cavity with 1.5-1.8 Å. Structural analysis and comparisons with other ?- and ?-class members suggest a catalytic mechanism in which the movements of Tyr-88 are important for the CO(2)-HCO(3)(-) interconversion, whereas a structurally conserved water molecule that bridges residues Tyr-88 and Gln-38, seems important for proton transfer, linking water molecules from the zinc-bound water to His-92 and buffer molecules.

| S-EPMC3230598 | biostudies-literature

Effects of cryoprotectants on the structure and thermostability of the human carbonic anhydrase II-acetazolamide complex.

Project description:Protein X-ray crystallography has seen a progressive shift from data collection at cool/room temperature (277-298 K) to data collection at cryotemperature (100 K) because of its ease of crystal preparation and the lessening of the detrimental effects of radiation-induced crystal damage, with 20-25%(v/v) glycerol (GOL) being the preferred choice of cryoprotectant. Here, a case study of the effects of cryoprotectants on the kinetics of carbonic anhydrase II (CA II) and its inhibition by the clinically used inhibitor acetazolamide (AZM) is presented. Comparative studies of crystal structure, kinetics, inhibition and thermostability were performed on CA II and its complex with AZM in the presence of either GOL or sucrose. These results suggest that even though the cryoprotectant GOL was previously shown to be directly bound in the active site and to interact with AZM, it affects neither the thermostability of CA II nor the binding of AZM in the crystal structure or in solution. However, addition of GOL does affect the kinetics of CA II, presumably as it displaces the water proton-transfer network in the active site.

| S-EPMC3640473 | biostudies-literature

High-resolution structure of human carbonic anhydrase II complexed with acetazolamide reveals insights into inhibitor drug design.

Project description:The crystal structure of human carbonic anhydrase II (CA II) complexed with the inhibitor acetazolamide (AZM) has been determined at 1.1 A resolution and refined to an R(cryst) of 11.2% and an R(free) of 14.7%. As observed in previous CA II-inhibitor complexes, AZM binds directly to the zinc and makes several key interactions with active-site residues. The high-resolution data also showed a glycerol molecule adjacent to the AZM in the active site and two additional AZMs that are adventitiously bound on the surface of the enzyme. The co-binding of AZM and glycerol in the active site demonstrate that given an appropriate ring orientation and substituents, an isozyme-specific CA inhibitor may be developed.

| S-EPMC2765883 | biostudies-literature

Structure-Activity Relationship Studies of Acetazolamide-Based Carbonic Anhydrase Inhibitors with Activity against <i>Neisseria gonorrhoeae</i>.

Project description:Neisseria gonorrhoeae is an urgent threat to public health in the United States and around the world. Many of the current classes of antibiotics to treat N. gonorrhoeae infection are quickly becoming obsolete due to increased rates of resistance. Thus, there is a critical need for alternative antimicrobial targets and new chemical entities. Our team has repurposed the FDA-approved carbonic anhydrase inhibitor scaffold of acetazolamide to target N. gonorrhoeae and the bacteria's essential carbonic anhydrase, NgCA. This study established both structure-activity and structure-property relationships that contribute to both antimicrobial activity and NgCA activity. This ultimately led to molecules 20 and 23, which displayed minimum inhibitory concentration values as low as 0.25 μg/mL equating to an 8- to 16-fold improvement in antigonococcal activity compared to acetazolamide. These analogues were determined to be bacteriostatic against the pathogen and likely on-target against NgCA. Additionally, they did not exhibit any detrimental effects in cellular toxicity assays against both a human endocervical (End1/E6E7) cell line or colorectal adenocarcinoma cell line (Caco-2) at concentrations up to 128 μg/mL. Taken together, this study presents a class of antigonococcal agents with the potential to be advanced for further evaluation in N. gonorrhoeae infection models.

| S-EPMC8317129 | biostudies-literature

Carbonic anhydrase activity in mammalian skeletal and cardiac muscle.

Project description:1. The presence of extravascular carbonic anhydrase activity in skeletal muscle, and its absence from cardiac muscle, were demonstrated in the rat. 2. The activity in skeletal muscle is approximately correlated with the proportion of dark fibres present in the middle fibre bundles.

| S-EPMC1183806 | biostudies-other

carbonic anhydrase (1 or 2) simple or double mutants-Comparative transcriptome analysis between carbonic anhydrase mutants and wild type Arabidopsis

Project description:cea05-01_carbonic-anhydrase - carbonic anhydrase (1 or 2) simple or double mutants - Identification of genes differentially expressed in leaves of single CA1 and CA2 T-DNA insertional mutants and in the corresponding double mutant vs wild type - CA1 (At3g01500) and CA2 (At5g14740) T-DNA insertional mutant lines, the double (CA1+CA2) mutant and wild type Arabidopsis seeds were sown in soil in a phytotron. Leaves were harvested 40 days later for RNA extraction

2012-03-25 | GSE36625 | GEO

Carbonic anhydrase in skeletal and cardiac muscle from rabbit and rat.

Project description:We have studied the distribution of carbonic anhydrases (CA) in several skeletal muscles of the hindlimb of rabbits and rats and in cardiac muscle of the rabbit. To remove erythrocyte CA, hindlimbs and hearts were thoroughly perfused with dextran solution, and the effectiveness of the perfusion was in most cases assessed by determining the contamination of the muscles with radioisotopes that had been used to label the erythrocytes before the perfusion was started. We observed three forms of CA: (1) cytosolic (sulphonamide-resistant) CA III; (2) a cytosolic sulphonamide-sensitive CA, probably isoenzyme II; (3) a membrane-bound form that was extracted from the particulate fraction using Triton X-100. These CA isoforms were distributed as follows. (1) CA III is located in the cytoplasm of slow, oxidative skeletal muscles and is absent from or low in fast skeletal and cardiac muscle; this holds for rabbits and rats and is identical with the pattern previously described for several other species. (2) The cytosolic sulphonamide-sensitive CA is present in fast rabbit muscles and absent from slow muscles of this species. In contrast, all skeletal muscles of the rat studied here lack, or possess only very low, activity of this isoenzyme. (3) The membrane-bound form of CA is present in all rabbit muscles studied; its activity appears somewhat higher in fast than in slow skeletal muscles. (4) Cardiac muscle constitutes an exception among all striated muscles of the rabbit as it possesses no form of cytosolic CA but a high activity of the membrane-bound form.

| S-EPMC1130903 | biostudies-other

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