Interaction of anions with a newly characterized alpha carbonic anhydrase from Halomonas sp

A new carbonic anhydrase identified in the Gram-negative bacterium (Chromohalobacter sp.) and the interaction of anions with the enzyme

In this study, the characterization and inhibition characteristic of α-class carbonic anhydrase from Chromohalobacter (ChCA) was documented for the first time. The carbonic anhydrase enzyme had 47.77% yield and 54.45-fold purity. The specific activity of the enzyme was determined as 318.52 U/mg proteins. Alternative substrate (4-nitrophenyl trifluoroacetate, 4-nitrophenyl phosphate, 4-nitrophenyl sulphate and 4-nitrophenyl acetate) were tested for the enzyme. K_M and V_max values for 4-nitrophenyl acetate were 4.57 mM and 4.29 EU/mL and for 4-nitrophenyl trifluoroacetate were 2.39 mM and 2.41 EU/mL. The anions, Cl^-, NO₂^-, NO₃^-, Br^-, ClO₃^-, ClO₄^-, I^-, CO₃^2- and SO₄^2-, inhibited the ChCA hydratase activity. Among nine anions, the strongest inhibitor activities were obtained with micro molar concentrations of NO₂^-, NO₃^-, Br^-, I^-, CO₃^2- (K_I values of 160-255 μM). Other four anions tested (Cl^-, ClO₃^-, ClO₄^- and SO₄^2-) showed moderate inhibitory activities (K_I values of 680-813.5 μM). The results obtained demonstrate that the anions we tested inhibit the Chromohalobacter CA (ChCA) enzyme as in other α-CAs in mammals; however, the susceptibility of ChCA resulted from anions differed significantly from that of other organism CAs.

Design, synthesis and molecular modelling studies of some pyrazole derivatives as carbonic anhydrase inhibitors

In this study, newly synthesised compounds 6, 8, 10 and other compounds (1-5, 7 and 9) and their inhibitory properties against the human isoforms hCA I and hCA II were reported for the first time. Compounds 1-10 showed effective inhibition profiles with KI values in the range of 5.13-16.9 nM for hCA I and of 11.77-67.39 nM against hCA II, respectively. Molecular docking studies were also performed with Glide XP to get insight into the inhibitory activity and to evaluate the binding modes of the synthesised compounds to hCA I and II. More rigorous binding energy calculations using MM-GBSA protocol which agreed well with observed activities were then performed to improve the docking scores. Results of in silico calculations showed that all compounds obey drug likeness properties. The new compounds reported here might be promising lead compounds for the development of new potent inhibitors as alternatives to classical hCA inhibitors.

Study of glycation process of human carbonic anhydrase II as well as investigation concerning inhibitory influence of 3-beta-hydroxybutyrate on it

Glycation is a non-enzymatic reaction between carbonyl groups in sugar and free amino groups in proteins. This reaction leads to changes in structure and functions of proteins in which the advanced glycation end products (AGEs) are the final outcome and cause many complications in diabetic patients. We herein examined the effect of fasting on the glycation process of human Carbonic anhydrase II under physiological conditions (37 °C and pH 7.4) employing various techniques, including Ultraviolet-visible spectroscopy, fluorescence spectroscopy and CD Spectroscopy. We found an increased 3-beta-hydroxybutyrate upon fasting. We studied various samples of control carbonic anhydrase (without glucose and 3-beta-hydroxybutyrate), carbonic anhydrase with glucose, carbonic anhydrase treated with 3-beta-hydroxybutyrate (BHB) and carbonic anhydrase along with glucose and 3-beta-hydroxybutyrate. The samples were incubated for 35 days under physiological conditions. Our results indicated that 3-beta-hydroxybutyrate inhibited the glycation process, decreased glucose binding to the protein, prevented the formation of AGEs, and modified the enzyme activity. Our findings would open new windows toward the enzymatic procedure which would have profound implication in understanding the diabetes mechanisms.

Characterization of marine bacterial carbonic anhydrase and their CO2 sequestration abilities based on a soil microcosm

The novel technology of biological carbon sequestration using microbial enzymes have numerous advantages over conventional sequestration strategies. In the present study, extracellular carbonic anhydrase (CA) producing bacteria were isolated from water samples in the Arabian Sea, India. A potential isolate, Bacillus safensis isolate AS-75 was identified based on 16S rDNA sequence analysis. The culture conditions suitable for CA production were 32 °C incubation temperature with 4% NaCl and 10 mM Zn supplementation. Experimental optimization of culture conditions enhanced enzyme activity to 265 U mL^-1. CA specific gene was characterized and based on the analysis, the CA of B. safensis isolate AS-75 was a leucine (11.3%) with α-helices as the dominant component in its secondary structure. Based on soil microcosm studies, CA could sequester CO₂ by 95.4% ± 0.11% in sterilized soil with enzyme microcosm. Hence, the application of enzyme was found to be more effective in removing CO₂.

Carbonic anhydrase inhibitory properties of some uracil derivatives

Inhibitors of carbonic anhydrase (CA) have been carried out in many therapeutic applications, especially antiglaucoma activity. In this study, we investigated some uracil derivatives (4–12) to inhibit human CA I (hCA I) and II (hCA II) isoenzymes. The K_I values of the compounds 4–12 are in the range of 0.085–428 µM for hCA I and of 0.1715–645 µM against hCA II, respectively. It is concluded from the kinetic investigations, all compounds used in the study act as competitive inhibitors with substrate, 4-NPA. Uracil derivatives are emerging agents for the inhibiton of carbonic anhydrase which could be used in biomedicine.

Synthesis and carbonic anhydrase inhibitory properties of novel chalcone substituted benzenesulfonamides

Carbonic anhydrases (CAs, EC 4.2.1.1) are crucial metalloenzymes involved in many bioprocesses, through catalysis of the reversible hydration/dehydration process of CO2/HCO3-. The inhibition of human CA isoforms I and II with a new series of sulfonamide derivatives incorporating substituted chalcone moieties were studied in this study. All these newly synthesized sulfonamides demonstrated important inhibitory profiles to these CA isoforms with KIs in the range of 9.88 to 55.43nM, making these compounds interesting leads, with potential applications in medicinal chemistry.

Anion inhibition profiles of the complete domain of the η-carbonic anhydrase from Plasmodium falciparum

We have cloned, purified and investigated the catalytic activity and anion inhibition profiles of a full catalytic domain (358 amino acid residues) carbonic anhydrase (CA, EC 4.2.1.1) from Plasmodium falciparum, PfCAdom, an enzyme belonging to the η-CA class and identified in the genome of the malaria-producing protozoa. A truncated such enzyme, PfCA1, containing 235 residues was investigated earlier for its catalytic and inhibition profiles. The two enzymes were efficient catalysts for CO2 hydration: PfCAdom showed a kcat of 3.8×10(5)s(-1) and kcat/Km of 7.2×10(7)M(-1)×s(-1), whereas PfCA showed a lower activity compared to PfCAdom, with a kcat of 1.4×10(5)s(-1) and kcat/Km of 5.4×10(6)M(-1)×s(-1). PfCAdom was generally less inhibited by most anions and small molecules compared to PfCA1. The best PfCAdom inhibitors were sulfamide, sulfamic acid, phenylboronic acid and phenylarsonic acid, which showed KIs in the range of 9-68μM, followed by bicarbonate, hydrogensulfide, stannate and N,N-diethyldithiocarbamate, which were submillimolar inhibitors, with KIs in the range of 0.53-0.97mM. Malaria parasites CA inhibition was proposed as a new strategy to develop antimalarial drugs, with a novel mechanism of action.

Synthesis and inhibitory properties of some carbamates on carbonic anhydrase and acetylcholine esterase

A series of carbamate derivatives were synthesized and their carbonic anhydrase I and II isoenzymes and acetylcholinesterase enzyme (AChE) inhibitory effects were investigated. All carbamates were synthesized from the corresponding carboxylic acids via the Curtius reactions of the acids with diphenyl phosphoryl azide followed by addition of benzyl alcohol. The carbamates were determined to be very good inhibitors against for AChE and hCA I, and II isoenzymes. AChE inhibition was determined in the range 0.209-0.291 nM. On the other hand, tacrine, which is used in the treatment of Alzheimer's disease possessed lower inhibition effect (Ki: 0.398 nM). Also, hCA I and II isoenzymes were effectively inhibited by the carbamates, with inhibition constants (Ki) in the range of 4.49-5.61 nM for hCA I, and 4.94-7.66 nM for hCA II, respectively. Acetazolamide, which was clinically used carbonic anhydrase (CA) inhibitor demonstrated Ki values of 281.33 nM for hCA I and 9.07 nM for hCA II. The results clearly showed that AChE and both CA isoenzymes were effectively inhibited by carbamates at the low nanomolar levels.