skip to main content
Primo Search
Search in: Busca Geral
Tipo de recurso Mostra resultados com: Mostra resultados com: Índice

Proton Transporting Enzymes at the Tonoplast of Leaf Cells of the CAM Plant Kalanchoë daigremontiana. II. The Pyrophosphatase

Marquardt, Gisela ; Lüttge, Ulrich

Journal of Plant Physiology, 1987, Vol.129(3), pp.269-286 [Periódico revisado por pares]

Texto completo disponível

Citações Citado por
  • Título:
    Proton Transporting Enzymes at the Tonoplast of Leaf Cells of the CAM Plant Kalanchoë daigremontiana. II. The Pyrophosphatase
  • Autor: Marquardt, Gisela ; Lüttge, Ulrich
  • Assuntos: Kalanchoë Daigremontiana ; Crassulacean Acid Metabolism ; PP I -Ase ; Proton Transport ; Tonoplast ; BSA ; Btp ; Cam ; Caps ; Dtt ; Edta ; Hepes ; IDA ; Mes ; Pi ; Ppi ; Pvp ; SDS ; Tricin ; Tris ; △Μ H +
  • É parte de: Journal of Plant Physiology, 1987, Vol.129(3), pp.269-286
  • Descrição: A purified fraction of tonoplast vesicles was obtained from homogenates of isolated mesophyll protoplasts of the CAM plant Kalanchoë daigremontiana by discontinuous sucrose-gradient centrifugation. The tonoplast vesicles showed pyrophosphate (PPi)-hydrolysis activity and PPi dependent H + uptake as measured by quinacrine-fluorescence quenching. The pH optimum of PPi hydrolysis was broad (pH 7.5 - 8.5) depending on the ionic composition of the medium, but the pH optimum of H + transport was very distinct at pH 8.2 - 8.7. PPi hydrolysis and H+ transport showed an absolute requirement for K + (Km for PPi hydrolysis 6 mM KCI, for H + transport 54 mM KCI), which could only be replaced by Rb +. The sequence of effectiveness of alkali cations was K + = Rb +>Cs +>Na +>Li +. Malate and chloride were ineffective. Slowly permeating sulphate anions and non-permeating iminodiacetate anions were inhibitory. Nitrate did not affect PPi hydrolysis but stimulated H+ transport. A high excess of Me' over the substrate PPi was required. At saturating concentrations of PPi (0.2 mM) up to 1 mM Mgt + was necessary for optimum activity. Half saturation was about 0.50 mM MgS04 and 0.02 to 0.03 mM PPi both for PPi hydrolysis and H+ transport. Other divalent cations (Zn 2 +, Cat +, Cue +) were ineffective in replacing Mg 2 +, and Mn 2 + was inhibitory causing H + efflux from preloaded tonoplast vesicles. These properties of the vacuolar PPi ase are compared with those of the vacuolar ATPase of K. daigremontiana and the possible role of a synergistic action of the two H +-transporting enzymes in the regulation of CAM is discussed.
  • Idioma: Inglês

Buscando em bases de dados remotas. Favor aguardar.