Studies on the carbonic anhydrase activity in Synechocystis PCC6803 wild type and an acetazolamide-resistant mutant

1991 ◽  
Vol 69 (5) ◽  
pp. 1103-1108 ◽  
Author(s):  
S. Bedu ◽  
F. Joset
Keyword(s):  
Carbonic Anhydrase ◽  
Inorganic Carbon ◽  
Physiological Role ◽  
Resistant Mutant ◽  
Carbonic Anhydrase Activity ◽  
Wild Type ◽  
Synechocystis Pcc6803 ◽  
Physiological Analysis ◽  
Carbon Concentrations

The problem of the role and the localization of carbonic anhydrase activity in cyanobacteria has been addressed by two approaches using strain Synechocystis PCC6803. Physiological analysis of the differential effects of carbonic anhydrase inhibitors on the entry and accumulation of CO2 in cells grown under low or high inorganic carbon concentrations and determination of carbonic anhydrase activities in cellular subfractions led to the hypothesis of the presence of two different enzymes in this strain. This conclusion is compatible with current models. Only the internal enzyme could be regulated by variations of the external inorganic carbon concentrations. A parallel analysis of a mutant of this strain resistant to the inhibitor acetazolamide supported the hypothesis of the presence of two enzymes. This clone would be selectively impaired in the carbonic anhydrase activity involved in the maintenance of the internal CO2 pool, while its transport capacity is unchanged. Key words: carbonic anhydrase, physiological role, localization, inhibitors, cyanobacteria, mutant.

A new chloroplast envelope carbonic anhydrase activity is induced during acclimation to low inorganic carbon concentrations in Chlamydomonas reinhardtii

Planta ◽  
2001 ◽  
Vol 213 (2) ◽  
pp. 286-295 ◽  
Author(s):  
Arsenio Villarejo ◽  
Norbert Rolland ◽  
Flor Martínez ◽  
Dieter F. Sültemeyer
Keyword(s):  
Carbonic Anhydrase ◽  
Chlamydomonas Reinhardtii ◽  
Inorganic Carbon ◽  
Carbonic Anhydrase Activity ◽  
Chloroplast Envelope ◽  
Carbon Concentrations

Fractionation of carbonic anhydrase activity in Gracilaria sp. (Rhodophyta) and Enteromorpha intestinalis (Chlorophyta): changes in the extracellular activity in response to inorganic carbon levels

2000 ◽  
Vol 27 (12) ◽  
pp. 1161 ◽  
Author(s):  
Jesús R. Andría ◽  
Juan J. Vergara ◽  
J. Lucas Pérez-Lloréns
Keyword(s):  
Carbonic Anhydrase ◽  
Inorganic Carbon ◽  
Soluble Fraction ◽  
Total Activity ◽  
Carbonic Anhydrase Activity ◽  
Enteromorpha Intestinalis ◽  
Short Term ◽  
Carbon Availability ◽  
Species Specific ◽  
Extracellular Activity

The presence of different carbonic anhydrase (EC 4.2.1.1) activities has been investigated in the intertidal macroalgae Gracilaria sp. and Enteromorpha intestinalis (L.) Nees by using fractionation techniques. Activities, measured potentiometrically, were recorded for all fractions in both species, including those containing proteins associated with chloroplast membranes. In Gracilaria sp., most of the total activity was present in the soluble fraction, while similar activities were obtained for all fractions in E. intestinalis. By using inhibitors with a different capacity to enter the cell (acetazolamide and 6-ethoxyzolamide, inhibitors of external and total activity, respectively), a surface-accessible location was indicated for a high proportion of the soluble activity obtained in Gracilaria sp. In E. intestinalis, the inhibitor assays showed a substantial dependence of photosynthesis on intracellular activity. The short-term regulation of the extracellular activity in response to inorganic carbon availability was also examined in both macroalgae. Rapid repression (after 2 h) of the activity was recorded when Gracilaria sp. was transferred from limited to replete carbon conditions, while a fairly constant activity was recorded for E. intestinalis. In contrast, an increase of external activity was obtained for both macroalgae after being transferred to carbon-limited conditions, this response being more pronounced in E. intestinalis. Our results suggest the occurrence of a species-specific carbonic anhydrase system.

scholarly journals In vitro analysis of human immunodeficiency virus type 1 resistance to nevirapine and fitness determination of resistant variants

2002 ◽  
Vol 83 (1) ◽  
pp. 93-101 ◽  
Author(s):  
Maria Dolores Iglesias-Ussel ◽  
Concepción Casado ◽  
Eloísa Yuste ◽  
Isabel Olivares ◽  
Cecilio López-Galíndez
Keyword(s):  
Fold Increase ◽  
Resistant Mutant ◽  
Wild Type ◽  
Resistance Mutations ◽  
Phenotypic Resistance ◽  
Drug Concentrations ◽  
Immunodeficiency Virus ◽  
Vitro Analysis

Nevirapine-resistant variants were generated by serial passages in MT-2 cells in the presence of increasing drug concentrations. In passage 5, mutations V106A, Y181C and G190A were detected in the global population, associated with a 100-fold susceptibility decrease. Sequence analysis of biological clones obtained from passage 5 and subsequent passages showed that single mutants, detected in first passages, were progressively replaced in passage 15 by double mutants, correlating with a 500-fold increase in phenotypic resistance. Fitness determination of single mutants confirmed that, in the presence of nevirapine, every variant was more fit than wild-type with a fitness order Y181C>V106A>G190A>wild-type. Unexpectedly, in the absence of the drug, the Y181C resistant mutant was more fit than wild-type, with a fitness gradient Y181C>wild-type >G106A⩾V190A. Using a molecular clone in which the Y181C mutation was introduced by in vitro mutagenesis, the greater fitness of the Y181C mutant was confirmed in new competition cultures. These data exemplify the role of resistance mutations on virus phenotype but also on virus evolution leading, occasionally, to resistant variants fitter than the wild-type in the absence of the drug.

scholarly journals Transgenic expression of carbonic anhydrase III in cardiac muscle demonstrates a mechanism to tolerate acidosis

2019 ◽  
Vol 317 (5) ◽  
pp. C922-C931 ◽  
Author(s):  
Han-Zhong Feng ◽  
J.-P. Jin
Keyword(s):  
Carbonic Anhydrase ◽  
Transgenic Mice ◽  
Intracellular Ph ◽  
Skeletal Muscles ◽  
Ex Vivo ◽  
Physiological Role ◽  
Wild Type Mouse ◽  
Carbonic Anhydrases ◽  
Wild Type ◽  
Carbonic Anhydrase Iii

Carbonic anhydrase III (CAIII) is abundant in liver, adipocytes, and skeletal muscles, but not heart. A cytosolic enzyme that catalyzes conversions between CO2 and [Formula: see text] in the regulation of intracellular pH, its physiological role in myocytes is not fully understood. Mouse skeletal muscles lacking CAIII showed lower intracellular pH during fatigue, suggesting its function in stress tolerance. We created transgenic mice expressing CAIII in cardiomyocytes that lack endogenous CAIII. The transgenic mice showed normal cardiac development and life span under nonstress conditions. Studies of ex vivo working hearts under normal and acidotic conditions demonstrated that the transgenic and wild-type mouse hearts had similar pumping functions under normal pH. At acidotic pH, however, CAIII transgenic mouse hearts showed significantly less decrease in cardiac function than that of wild-type control as shown by higher ventricular pressure development, systolic and diastolic velocities, and stroke volume via elongating the time of diastolic ejection. In addition to the effect of introducing CAIII into cardiomyocytes on maintaining homeostasis to counter acidotic stress, the results demonstrate the role of carbonic anhydrases in maintaining intracellular pH in muscle cells as a potential mechanism to treat heart failure.

Extracellular carbonic anhydrase of Chlamydomonas reinhardtii: localization, structural properties, and catalytic properties

1991 ◽  
Vol 69 (5) ◽  
pp. 1079-1087 ◽  
Author(s):  
H. David Husic
Keyword(s):  
Plasma Membrane ◽  
Carbonic Anhydrase ◽  
Chlamydomonas Reinhardtii ◽  
Inorganic Carbon ◽  
Catalytic Properties ◽  
Physiological Role ◽  
Carbon Utilization ◽  
Unicellular Green Alga ◽  
Inorganic Carbon Utilization ◽  
Inorganic Carbon Acquisition

In the unicellular green alga Chlamydomonas reinhardtii, a form of the enzyme carbonic anhydrase that is localized outside of the plasma membrane is an inducible component of a system that is involved in inorganic carbon acquisition and concentration from the growth medium. This article contains a review and analysis of the current literature regarding the extracellular carbonic anhydrase from Chlamydomonas reinhardtii and presents some new studies on its extracellular localization, physiological role in inorganic carbon acquisition, and some of the structural and catalytic properties of the enzyme. Key words: carbonic anhydrase, Chlamydomonas reinhardtii, inorganic carbon utilization.

Determination of carbonic anhydrase activity by a pCO2 sensor

1990 ◽  
Vol 185 (2) ◽  
pp. 254-264 ◽  
Author(s):  
Claudio Botrè ◽  
Francesco Botrè
Keyword(s):  
Carbonic Anhydrase ◽  
Carbonic Anhydrase Activity

scholarly journals Carbonic Anhydrase Activity in Isolated Chloroplasts of Wild-Type and High-CO2-Dependent Mutants of Chlamydomonas reinhardtii as Studied by a New Assay

1994 ◽  
Vol 105 (4) ◽  
pp. 1197-1202 ◽  
Author(s):  
G. L. Katzman ◽  
S. J. Carlson ◽  
Y. Marcus ◽  
J. V. Moroney ◽  
R. K. Togasaki
Keyword(s):  
Carbonic Anhydrase ◽  
Chlamydomonas Reinhardtii ◽  
Carbonic Anhydrase Activity ◽  
Wild Type ◽  
High Co2 ◽  
Isolated Chloroplasts

Inorganic carbon transport in some marine microalgal species

1991 ◽  
Vol 69 (5) ◽  
pp. 1032-1039 ◽  
Author(s):  
M. J. Merrett
Keyword(s):  
Carbonic Anhydrase ◽  
Inorganic Carbon ◽  
Silicone Oil ◽  
Ph Regulation ◽  
Carbonic Anhydrase Activity ◽  
Carbon Accumulation ◽  
Bicarbonate Transport ◽  
High Affinity ◽  
Inorganic Carbon Transport ◽  
Carbon Transport

Inorganic carbon transport was investigated in a range of marine microalgae. A small-celled strain of Stichococcus bacillaris, containing appreciable carbonic anhydrase activity, showed a high affinity for CO2, while measurement of the internal inorganic carbon pool by the silicone oil layer centrifugal filtering technique showed cells concentrated inorganic carbon up to 20-fold in relation to the external medium at pH 5.0 but not pH 8.3. The addition of 14CO2 or H14CO3− to cells in short-term kinetic experiments at pH 8.3 confirmed that only CO2 provides the exogenous substrate for substantial inorganic carbon accumulation within the cell. High-affinity HCO3− transport in Phaeodactylum tricornutum and Porphyridium purpureum is dependent on sodium ions, while intracellular carbonic anhydrase increased the steady-state flux of CO2 from inside the plasmalemma to Rubisco. In the presence of HCO3− the intracellular pH in cells of P. purpureum is 7.1 but on carbon starvation the pH falls to 6.0. Ethoxyzolamide blocks bicarbonate-dependent alkalinization of the cytosol, confirming a central role for carbonic anhydrase–bicarbonate in cytosolic pH regulation. Carbonic anhydrase activity is pH dependent in P. purpureum so synergistic interaction between CO2 uptake and bicarbonate transport may occur.

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