caa a22 4500 477101933 CHVBK 20180405111544.0 cr unu---uuuuu 170330e19960601xx s 000 0 eng 10.1007/BF00196557 doi (NATIONALLICENCE)springer-10.1007/BF00196557 Intracellular carbonic anhydrase activities in Dunaliella tertiolecta (Butcher) and Chlamydomonas reinhardtii (Dangeard) in relation to inorganic carbon concentration during growth: further evidence for the existence of two distinct carbonic anhydrases associated with the chloroplasts [Elektronische Daten] [Gabi Amoroso, Claudia Weber, Dieter Sültemeyer, Heinrich Fock] Using mass-spectrometric measurements of 18O exchange from 13C18O2 intracellular carbonic anhydrase (CA) activity was investigated in the unicellular green algae Dunaliella tertiolecta and Chlamydomonas reinhardtii which were either grown on air enriched with 5% CO2 (high-Ci cells) or on air (low-Ci cells). In D. tertiolecta high- and low-Ci cells had detectable levels of internal CA activity when measured under in-vivo conditions and this activity could be split up into three distinct forms. One CA was not associated with the chloroplasts, while two isozymes were found to be located within the plastids. The activities of all intracellular CAs were always about twofold higher in low than in high-Ci cells of D. tertiolecta and the chloroplastic enzymes were completely induced within 4 h of adaptation to air. One of the chloroplastic CAs was found to be soluble the other was insoluble. In addition to the physical differences, MgSO4 in vitro caused a more than twofold stimulation of the soluble activity while the insoluble form of CA remained rather unaffected. In C. reinhardtii, MgSO4 increased the soluble CA activity by 346% and the concentration of MgSO4 required for half-maximum stimulation was between 10 and 15 mM. Again, the insoluble CA activity was not affected by MgSO4. Furthermore, the soluble isoenzyme was considerably more sensitive to ethoxyzolamide, a potent inhibitor of CA, than the insoluble enzyme. The concentration of inhibitor causing 50% inhibition of soluble CA activity was 110 and 85 μM ethoxyzolamide for D. tertiolecta and C. reinhardtii, respectively. From these data we conclude that the two chloroplast-associated CAs are distinct enzymes. Springer-Verlag, 1996 Carbonic anhydrase nationallicence Chlamydomonas nationallicence CO2 concentrating mechanism nationallicence Dunaliella nationallicence Photosynthesis nationallicence AZA : acetazolamide nationallicence Ci : inorganic carbon (HCO 3 − + CO2) nationallicence CA : carbonic anhydrase nationallicence cCAinsol : insoluble chloroplastic CA nationallicence cCAsol : soluble chloroplastic CA nationallicence CCM : CO2 concentrating mechanism nationallicence EZA : ethoxyzolamide nationallicence high-Ci cells : cells grown in air enriched with 5% CO2 nationallicence I50 : inhibitor concentration required for 50% inhibition nationallicence K1/2 : concentration required for half-maximal response nationallicence low-Ci cells : cells grown in air (0.035% CO2) nationallicence Rubisco : ribulose-1,5-bisphosphate carboxylase/oxygenase nationallicence Amoroso Gabi Fachbereich Biologie, Universität Kaiserslautern, Postfach 3049, D-67653, Kaiserslautern, Germany aut Weber Claudia Fachbereich Biologie, Universität Kaiserslautern, Postfach 3049, D-67653, Kaiserslautern, Germany aut Sültemeyer Dieter Fachbereich Biologie, Universität Kaiserslautern, Postfach 3049, D-67653, Kaiserslautern, Germany aut Fock Heinrich Fachbereich Biologie, Universität Kaiserslautern, Postfach 3049, D-67653, Kaiserslautern, Germany aut Planta Springer-Verlag 199/2(1996-06-01), 177-184 0032-0935 199:2<177 1996 199 425 https://doi.org/10.1007/BF00196557 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00196557 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Amoroso Gabi Fachbereich Biologie, Universität Kaiserslautern, Postfach 3049, D-67653, Kaiserslautern, Germany aut NATIONALLICENCE 700 1- Weber Claudia Fachbereich Biologie, Universität Kaiserslautern, Postfach 3049, D-67653, Kaiserslautern, Germany aut NATIONALLICENCE 700 1- Sültemeyer Dieter Fachbereich Biologie, Universität Kaiserslautern, Postfach 3049, D-67653, Kaiserslautern, Germany aut NATIONALLICENCE 700 1- Fock Heinrich Fachbereich Biologie, Universität Kaiserslautern, Postfach 3049, D-67653, Kaiserslautern, Germany aut NATIONALLICENCE 773 0- Planta Springer-Verlag 199/2(1996-06-01), 177-184 0032-0935 199:2<177 1996 199 425 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer