caa a22 4500 397522029 CHVBK 20180308164635.0 cr unu---uuuuu 161202e199504 xx s 000 0 eng 10.1093/jxb/46.4.383 doi (NATIONALLICENCE)oxford-10.1093/jxb/46.4.383 Characterization of the vacuolar-type H+-ATPase from guard cell protoplasts of Commelina [Elektronische Daten] [C.M. Willmer, G. Grammatikopoulos, G. LascÈve, A. Vavasseur] Characteristics of the vacuolar-type (V-type) H+-ATPase from guard cell protoplasts of Commelina communis L. were investigated using a linked enzyme assay and nitrate inhibition as a diagnostic indicator of the enzyme activity. ATPase activity was completely inhibited by about 50 mol m−3 nitrate and activity was optimal near pH 8.0. The temperature optimum for activity was about 37 °C and an Arrhenius plot indicated changes in activation energy for the ATPase at 15°C and possibly at about 30 °C. The enzyme was stimulated by Cl− while Ca2+ inhibited activity (l50 °= 1.5 mol m-3). The apparent Km (MgATP) was 0.62 mol m−3. Incubation of guard cell protoplasts for up to 5 h in 50 μM abscisic acid (ABA) or 25μM fusicoccin (FC) did not affect subsequent ATPase activity. In vitro assays with FC or ABA also did not affect enzyme activity. Activity was not affected by light or potassium ferricyanide, two factors which are known to influence stomatal activity. Beticoline was a potent inhibitor of activity (l50 = 50 μM) while DCCD was less effective (l50 = 90μM). On chlorophyll, protein and protoplast bases, V-type ATPase activity was greater in guard cell protoplasts than mesophyll cell protoplasts by ×66, ×13.9 and × 1.9, respectively. On a tonoplast surface area basis the enzyme activity was 5.6 times higher in guard cell protoplasts than in mesophyll cell protoplasts Thus, although the characteristics of the V-type, H +-ATPase of GCP are very similar to those found in other cell types, rates of activity and probably tonoplast enzyme density are much greater in guard cell protoplasts than mesophyll cell protoplasts of C. communis which corresponds with the large and rapid ion fluxes across the tonoplast associated with stomatal movements © Oxford University Press Articles nationallicence Guard cell protoplasts nationallicence stomata nationallicence V-type H +-ATPase nationallicence Willmer C.M. Department of Biological and Molecular Sciences, University of Stirling Stirling FK9 4LA, UK aut Grammatikopoulos G. Department of Plant Physiology, University of Patras Patras, Greece aut LascÈve G. CEA, CEN Cadarache, DPVE 13108 St Paul lez Durance, France aut Vavasseur A. CEA, CEN Cadarache, DPVE 13108 St Paul lez Durance, France aut Journal of Experimental Botany Oxford University Press 46/4(1995-04), 383-389 0022-0957 46:4<383 1995 46 exbotj https://doi.org/10.1093/jxb/46.4.383 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1093/jxb/46.4.383 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Willmer C.M. Department of Biological and Molecular Sciences, University of Stirling Stirling FK9 4LA, UK aut NATIONALLICENCE 700 1- Grammatikopoulos G. Department of Plant Physiology, University of Patras Patras, Greece aut NATIONALLICENCE 700 1- LascÈve G. CEA, CEN Cadarache, DPVE 13108 St Paul lez Durance, France aut NATIONALLICENCE 700 1- Vavasseur A. CEA, CEN Cadarache, DPVE 13108 St Paul lez Durance, France aut NATIONALLICENCE 773 0- Journal of Experimental Botany Oxford University Press 46/4(1995-04), 383-389 0022-0957 46:4<383 1995 46 exbotj Metadata rights reserved CC BY-NC-4.0 http://creativecommons.org/licenses/by-nc/4.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-oxford