Enhanced recombinant Sulfurihydrogenibium yellowstonense carbonic anhydrase activity and thermostability by chaperone GroELS for carbon dioxide biomineralization

Chemical Controls on the Dissolution Kinetics of Calcite in Seawater

Biomineralization-based conversion of carbon dioxide to calcium carbonate using recombinant carbonic anhydrase

Efficient carbon dioxide sequestration by using recombinant carbonic anhydrase

Carbonic anhydrase enzymes: Likely targets for inhalational anesthetics

Objective:Carbonic anhydrase (CA), 6-phosphogluconate dehydrogenase (6PGD) andthioredoxin reductase (TrxR) enzymes are the essential biological molecules needed for metabolic processes in all livingcells. This study was designed to investigate the activities of CA, 6PGD andTrxR enzymes in the brain, kidney, liver, heart and testis tissues of the ratsexposed to Dox and morin. Methods:Male Wistar albino rats were randomly divided into three groups as control,morin and DOX, each of them containing 7 rats. At the end of the experimentalprocedure, CA, 6PGD and TrxR enzyme activities in tissues of rats weredetermined spectrophotometrically. Results:In our study, we observed that DOX activated CA enzyme in liver and kidneytissues while inhibiting CA enzyme in the other tissues, activated 6PGD enzyme in the kidney, liver and hearttissues, and inhibited the TrxR enzyme in all the tissues. In addition, morinactivated CA enzyme in the liver tissue while inhibiting CA enzyme in thebrain, heart and testis tissues. Morin activated 6PGD enzyme activity while it inhibited TrxR enzyme in all the tissues.Conclusion:The findings showed that doxorubicin and morin had similar properties in thetissues as to their effect on enzyme activities.

Carbon dioxide elimination by cardiomyocytes: a tale of high carbonic anhydrase activity and membrane permeability.

Bacterial extremo-α-carbonic anhydrases from deep-sea hydrothermal vents as potential biocatalysts for CO2 sequestration

Scaling down recombinant carbonic anhydrase isolation with immobilized metal ion chromatography (IMAC): Harnessing enzymatic carbon dioxide capture and mineralization

This project was aimed at obtaining process engineering and scale-up data at a laboratory scale to investigate the technical and economic feasibility of a patented post-combustion carbon dioxide (CO{sub 2}) capture process?the Integrated Vacuum Carbonate Absorption Process (IVCAP). Unique features of the IVCAP include its ability to be fully-integrated with the power plant?s steam cycle and potential for combined sulfur dioxide (SO{sub 2}) removal and CO{sub 2} capture. Theoretical and experimental studies of this project were aimed at answering three major technical questions: 1) What additives can effectively reduce the water vapor saturation pressure and energy requirement for water vaporization in the vacuum stripper of the IVCAP? 2) What catalysts can promote CO{sub 2} absorption into the potassium carbonate (PC) solution to achieve an overall absorption rate comparable to monoethanolamine (MEA) and are the catalysts stable at the IVCAP conditions and in the flue gas environment? 3) Are any process modifications needed to combine SO{sub 2} and CO{sub 2} removal in the IVCAP? Lab-scale experiments and thermodynamic and process simulation studies performed to obtain detailed information pertinent to the above three technical questions produced the following results: 1) Two additives were identified that lower the saturation pressure of water vapor over the PC solution by about 20%. 2) The carbonic anhydrase (CA) enzyme was identified as the most effective catalyst for promoting CO{sub 2} absorption. The absorption rate into the CO{sub 2}-lean PC solution promoted with 300 mg/L CA was several times slower than the corresponding 5 M MEA solution, but absorption into the CO{sub 2}-rich PC solution was comparable to the CO{sub 2}-rich MEA solution. The tested CA enzymes demonstrated excellent resistance to major flue gas impurities. A technical-grade CA enzyme was stable at 40{degrees}C (104{degrees}F) over a six-month test period, while its half-life was about two months at 50{degrees}C (122{degrees}F). Enzyme immobilization improved the CA enzyme?s thermal stability by up to three times compared to its free counterpart. 3) Two process modifications were proposed to improve the technical performance of the IVCAP for combined SO{sub 2} removal and CO{sub 2} capture. The results from a techno-economic study of a 528 MWe (gross) pulverized coal-fired, subcritical steam power plant revealed that the cost of CO{sub 2} avoidance with the IVCAP was about 30% lower than conventional MEA-based processes. The levelized cost of electricity (LCOE) of the IVCAP ranged from $40 to 46/MWh, an increase of 60 to 70% compared to a reference power plant without CO{sub 2} capture. The overall conclusion of this study is that the IVCAP is a technically feasible and economically more attractive process than available MEA-based processes. A scale-up study using the slipstream of an actual coal-derived flue gas and development of a more stable CA enzyme are recommended for future studies.

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.

We have previously demonstrated that melatonin and its analogue, 5-methoxycarbonylamino-N-acetyltryptamine (5-MCA-NAT), reduce intraocular pressure (IOP) in New Zealand rabbits. More recently, we have shown that 5-MCA-NAT can also regulate ciliary adrenoceptor gene expression. Like adrenoceptors, carbonic anhydrase (CA) enzymes are involved in aqueous humour secretion by the ocular ciliary epithelium. Moreover, CA enzymes have been reported to be regulated by melatonin. Hence, the aim of this study was to investigate whether the hypotensive effect of 5-MCA-NAT is also because of a regulation of CA genes and enzymes. Time course of 5-MCA-NAT effect on rabbit IOP was followed for 7 hr every day for up to 144 hr (6 days). 5-MCA-NAT reduced IOP, maximally by 51.30 ± 2.41% (at 3 hr), and the hypotensive effect was maintained for up to 96 hr with a single application. IOP studies with 5-MCA-NAT plus Trusopt(®) and immunohistochemical analysis confirmed that CA are molecular targets of 5-MCA-NAT. In addition, real-time quantitative PCR (qPCR) and immunocytochemical assays were performed to determine changes in CA2 (CAII) and CA12 (CAXII) expression in cultured rabbit nonpigmented ciliary epithelial cells (NPE) treated with 5-MCA-NAT. NPE cells showed a prominent decrease in both CA, at the mRNA and protein levels. These data confirm that the long-term hypotensive effect of 5-MCA-NAT is also due, to a down-regulation of CA2 (CAII) and CA12 (CAXII) expression.

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.

Carbon dioxide (CO2) is both an unavoidable waste product of aerobic carbohydrate metabolism and a fuel source for autotrophic and chemoautotrophic organisms. At biological pH, CO2 rapidly reacts with interstitial and intracellular water to form carbonic acid (H2CO3), that then dissociates into protons (H+) and bicarbonate (HCO3-). While CO2 and H+ readily diffuse across biological membranes, the majority of the CO2 in living tissues is in the membrane-impermeable form HCO3-. The enzyme carbonic anhydrase (CA) catalyzes the reversible hydration of CO2 with water to maintain an instantaneous equilibrium between these chemical species. CA is not only central to the transport and excretion of CO2 in animals (or uptake in autotrophic organisms), but is also indirectly involved in important physiological processes, such as osmoregulation and acid-base balance. The multiple functions of CA are a result of multiple isoforms that are localized to specific subcellular compartments/fractions. Furthermore, the level of CA activity in an organism can be induced to change in response to conditions in the ambient environment, and may also reflect the metabolic rate of the organism. This enzyme has been studied in cell and tissue types from numerous organisms, but has never been systematically characterized in squids. This dissertation examined CA activity in gill and mantle muscle among several cephalopod species in terms of aerobic mass-specific metabolic rates (MR), evolutionary relationships, and environmental conditions. It also compared the protein-specific activity of CA in the respiratory tissue reported in the literature for a broad array of invertebrates. The CA activity in gill and mantle muscle tissue from three squid species was measured to examine whether differences in activity may be related to phylogenetic relationships or environmental adaptations. The three squid species, Dosidicus gigas, Lolliguncula brevis, and Doryteuthis pealeii have similar MR but endure different physiological demands due to their respective environmental conditions. The largest member of family Ommastrephidae, Dosidicus gigas, undergoes diel vertical migrations into a well-defined oxygen minimum zone in the eastern Pacific. The brief squid, Lolliguncula brevis, is the only squid species that inhabits the wide-ranging abiotic conditions of estuarine waters. This species is in the same family as Doryteuthis pealeii, yet the latter requires narrower environmental parameters. For all three species the total CA activity was greater in gill tissue than in mantle muscle, but the activity in each tissue was statistically the same between these species. The distribution of CA isozymes within the subcellular compartments, however, was

During the early stages of development, most creatures are small enough to meet their metabolic demands by diffusion alone. However, as embryos grow they switch to circulatory systems and gas exchange to satisfy their metabolic requirements. A key molecular component of most circulator systems is the enzyme carbonic anhydrase (CA), which speeds up the conversion of carbon dioxide to soluble bicarbonate for transport. Katie Gilmour, from the University of Ottawa, explains that although the development of the oxygen delivery system is well understood, little is known about the development of the systems involved in carbon dioxide excretion. Intrigued by all aspects of carbon dioxide excretion involving CA, Gilmour and her collaborator Steve Perry were curious to know when a developing animal switches from gas exchange by diffusion to a circulatory system, and whether that is correlated with the expression of CA. Gilmour and Perry turned to the zebrafish to find the answer (p. 3837).‘One of the exciting possibilities of working in zebrafish is the capacity to work in very young fish,’ explains Gilmour. Teaming up with Andrew Esbaugh, Gilmour and Perry set out to measure when CA expression kicked in by measuring the relative amount of CA mRNA in zebrafish embryos and larvae, ranging from 3 h to 5 days postfertilisation. Knowing that zebrafish produce various different forms of CA, each specialised for specific physiological functions, Gilmour and Perry focused on the form involved in CO2 excretion in red blood cells (CAb) and another form, specialised in acid—base regulation found in almost all tissues (CAc). Using real-time PCR, the team saw that the expression levels of the red blood cell form of CA (CAb) were always higher than the more general form of the enzyme (CAc), and there was a substantial increase in CAb at 8 h postfertilisation. But would that correlate with the amount of CO2 that the embryos and larvae were excreting? Gilmour and Perry teamed up with honours student Kelli Thomas to find out.‘CO2 chemically reacts with water to give bicarbonate so you have to measure the total CO2 content, which is very finicky,’ says Gilmour. Thomas painstakingly sealed groups of embryos or larvae in a chamber for a period ranging from 20 to 90 min (depending on the age of the embryos/larvae), collected water samples at the beginning and end of the period and measured the total carbon dioxide levels with Gilmour's cantankerous Capni-Con 5. Calculating the CO2 levels relative to the water's oxygen levels, the team could see that the fish began excreting large amounts of CO2 at 48 h, around the time that they hatch. In fact the team were surprised to realise that, prior to hatching, CO2 excretion by the eggs was far less than O2 uptake. They must be storing CO2, although Gilmour and Perry are unsure where.Having found the point at which the larvae begin excreting CO2, Gilmour and Perry were keen to find out which type of CA was responsible for the massive increase in CO2 excretion. Using a molecular technique only available in zebrafish, the team were pleased to see that CAb was partially responsible for the increase in CO2 excretion. But they were amazed to see that CAc was involved in CO2 excretion too. ‘That isn't the case in adult animals,' says Gilmour.Having found that CAb is a key player in CO2 excretion, Perry and Gilmour are keen to discover whether red blood cells are actively involved in CO2 excretion at 48 h, which is long before they are essential for oxygen transport, at 14 days.

Summary1. Carbonic anhydrases from vertebrates, plants and bacteria have molecular weights of 30,000 (or multiples thereof), contain one zinc atom per 30,000 molecular weight, and are inhibited by acetazolamide and related compounds.2. In mammals, there are two major isoenzymes of carbonic anhydrase. The so‐called ‘high activity’ carbonic anhydrase possesses a carbon dioxide‐hydratase activity many times (in the case of the guinea‐pig isoenzymes, 18 times) that of the ‘low activity’ isoenzyme.3. The mammalian isoenzymes differ from one another in their amino‐acid compositions (the difference in serine contents being a consistent finding in a number of species), in their physical properties (isoelectric pH, retention by ion‐exchange resins, electrophoretic mobility) and in their kinetic properties.4. Mammalian carbonic anhydrases also catalyse the hydrolysis of some esters and the hydration of aldehydes. Their relative activities with these other substrates may be substantially different from their relative activities with carbon dioxide as substrate. The discovery that carbonic anhydrase may also catalyse other reactions raises the possibility that the enzyme may have other roles in metabolic pathways (e.g., in certain dehydrogenation reactions).5. In plants, the role of carbonic anhydrase may be to catalyse the inter‐conversion of bicarbonate and carbon dioxide, to provide ‘carbon dioxide’ in the form appropriate for carbon‐fixing reactions. A similar role has been suggested for the carbonic anhydrase found in Neissariae.6. The carbonic anhydrase of vertebrates (the ‘high activity’ isoenzyme of mammals) is found in many ion‐transporting epithelia, but its role in them is still uncertain. It occurs in acid‐transporting epithelia such as the stomach and kidney, and also in certain bicarbonate‐transporting epithelia like the large intestine. There is, however, a poor correlation between the presence of the enzyme and the occurrence of acid or bicarbonate secretion. Thus there is little or no carbonic anhydrase in some tissues noted for their ability to secrete bicarbonate ions, such as the pancreas and ileum. Conversely, carbonic anhydrase‐containing tissues like the avian salt gland and the elasmobranch rectal gland form concentrated sodium chloride solutions which are of nearly neutral pH. The correlation between the distribution of carbonic anhydrase and the occurrence of active chloride transport appears similar to that between carbonic anhydrase and bicarbonate ion transport.7. While the red cells of most mammalian species so far studied contain both ‘high activity’ and ‘low activity’ isoenzymes, the latter is reported to be absent from the erythrocytes of sheep, ox and dog. Presumably the ‘low activity’ isoenzyme is not necessary for an adequate rate of carbon dioxide exchange to occur between tissues and lungs in these species.8. The ‘low activity’ isoenzyme is present in tissues other than blood, for example, the colon, caecum and ox rumen, and probably also, the gall bladder and kidney medulla. Its distribution differs markedly from that of the ‘high activity’ isoenzyme and presumably it has a particular functional importance of its own. It is not possible to define the role of the ‘low activity’ isoenzyme at present, but attention is drawn to the possibility that it is concerned in the handling of the products of microbial fermentation, such as ammonia and organic acids, by the large intestines and ruminant forestomach.My work on the isoenzymes of carbonic anhydrase was supported by a Medical Research Council Scholarship, and by an equipment grant to Dr D. S. Parsons. I am also grateful to Dr D. S. Parsons for his comments on the manuscript.