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Anhydrase Activity (anhydrase + activity)

Distribution by Scientific Domains
Life Sciences75%

Kinds of Anhydrase Activity

  • carbonic anhydrase activity
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    Selected Abstracts

    Composition and activity of external carbonic anhydrase of microalgae from karst lakes in China

    PHYCOLOGICAL RESEARCH, Issue 2 2008
    Yanyou Wu
    SUMMARY The species composition, the net photosynthetic O2 evolution rate and the activity of external carbonic anhydrase (CA) of microalgae from three reservoirs were studied. Carbonic anhydrase activity had a significant positive correlation with the density of Cyanobacteria in Lake Aha. Microalgae's carbonic anhydrase activity in Lakes Baihua and Hongfeng was related to the density of Chlorophyceae. The species abundances of microalgae in Lake Aha, Lake Baihua, and Lake Hongfeng were different. A relationship between carbonic anhydrase activity and net photosynthetic O2 evolution rate had also been established. Algae with external CA influenced the algal productivity. These results demonstrate the role of external CA in facilitating the availability of CO2 that limits the photosynthesis of microalgae in karst lakes in China. [source]

    Naturally low carbonic anhydrase activity in C4 and C3 plants limits discrimination against C18OO during photosynthesis

    PLANT CELL & ENVIRONMENT, Issue 9 2000
    J. S. Gillon
    ABSTRACT The 18O content of CO2 is a powerful tracer of photosynthetic activity at the ecosystem and global scale. Due to oxygen exchange between CO2 and 18O-enriched leaf water and retrodiffusion of most of this CO2 back to the atmosphere, leaves effectively discriminate against 18O during photosynthesis. Discrimination against 18O (,18O) is expected to be lower in C4 plants because of low ci and hence low retrodiffusing CO2 flux. C4 plants also generally show lower levels of carbonic anhydrase (CA) activities than C3 plants. Low CA may limit the extent of 18O exchange and further reduce ,18O. We investigated CO2,H2O isotopic equilibrium in plants with naturally low CA activity, including two C4 (Zea mays, Sorghum bicolor) and one C3 (Phragmites australis) species. The results confirmed experimentally the occurrence of low ,18O in C4, as well as in some C3, plants. Variations in CA activity and in the extent of CO2,H2O isotopic equilibrium (,eq) estimated from on-line measurements of ,18O showed large range of 0,100% isotopic equilibrium (,eq= 0,1). This was consistent with direct estimates based on assays of CA activity and measurements of CO2 concentrations and residence times in the leaves. The results demonstrate the potential usefulness of ,18O as indicator of CA activity in vivo. Sensitivity tests indicated also that the impact of ,eq< 1 (incomplete isotopic equilibrium) on 18O of atmospheric CO2 can be similar for C3 and C4 plants and in both cases it increases with natural enrichment of 18O in leaf water. [source]

    The K+,Cl, cotransporter KCC2 promotes GABAergic excitation in the mature rat hippocampus

    THE JOURNAL OF PHYSIOLOGY, Issue 9 2010
    Tero Viitanen
    GABAergic excitatory [K+]o transients can be readily evoked in the mature rat hippocampus by intense activation of GABAA receptors (GABAARs). Here we show that these [K+]o responses induced by high-frequency stimulation or GABAA agonist application are generated by the neuronal K+,Cl, cotransporter KCC2 and that the transporter-mediated KCl extrusion is critically dependent on the bicarbonate-driven accumulation of Cl, in pyramidal neurons. The mechanism underlying GABAergic [K+]o transients was studied in CA1 stratum pyramidale using intracellular sharp microelectrodes and extracellular ion-sensitive microelectrodes. The evoked [K+]o transients, as well as the associated afterdischarges, were strongly suppressed by 0.5,1 mm furosemide, a KCl cotransport inhibitor. Importantly, the GABAAR-mediated intrapyramidal accumulation of Cl,, as measured by monitoring the reversal potential of fused IPSPs, was unaffected by the drug. It was further confirmed that the reduction in the [K+]o transients was not due to effects of furosemide on the Na+ -dependent K+ -Cl, cotransporter NKCC1 or on intraneuronal carbonic anhydrase activity. Blocking potassium channels by Ba2+ enhanced [K+]o transients whereas pyramidal cell depolarizations were attenuated in further agreement with a lack of contribution by channel-mediated K+ efflux. The key role of the GABAAR channel-mediated anion fluxes in the generation of the [K+]o transients was examined in experiments where bicarbonate was replaced with formate. This anion substitution had no significant effect on the rate of Cl, accumulation, [K+]o response or afterdischarges. Our findings reveal a novel excitatory mode of action of KCC2 that can have substantial implications for the role of GABAergic transmission during ictal epileptiform activity. [source]

    High levels of intra-specific variation in the NG repeat region of the Pinctada maxima N66 organic matrix protein

    AQUACULTURE RESEARCH, Issue 9 2009
    Carolyn Smith-Keune
    Abstract There has been wide speculation about the functional importance, and potential contribution to the varying nacre characteristics of pearl oysters, of variation in the length of an asparagine,glycine-rich repeat domain (the NG region) within the key organic matrix proteins nacrein and N66. This speculation has centred on large inter-species differences in the length of the NG protein domain. We report for the first time the presence of significant intra-specific (allelic) polymorphism in both the length and the amino acid sequence of the NG repeat domain of N66 within both wild and hatchery populations of Pinctada maxima. We also detected the presence of a second putative N66-like locus within the P. maxima genome. Confirmation of gene expression of the various alleles at the two loci identified in P. maxima is now required, together with experimental testing of functional differences in the carbonic anhydrase activity of the alleles identified. [source]