caa a22 4500 477100406 CHVBK 20180405111539.0 cr unu---uuuuu 170330e19961001xx s 000 0 eng 10.1007/BF00208307 doi (NATIONALLICENCE)springer-10.1007/BF00208307 Regulation of nitrate reductase and phosphoenolpyruvate carboxylase activities in barley leaf protoplasts [Elektronische Daten] [Cathrine Lillo, Lucy Smith, Hugh Nimmo, Malcolm Wilkins] Barley leaf protoplasts were incubated in light or darkness in the presence of various inhibitors, metabolites or weak acids/bases. Nitrate reductase (NR) and phosphoenolpyruvate carboxylase (PEPCase) were rapidly extracted from the protoplasts and assayed under sub-optimal conditions, i.e. in the presence of Mg2+ and malate, respectively. Under these conditions changes in activities are thought to reflect changes in the phosphorylation states of the enzymes. The NR was activated by illumination to 90% of its maximal activity within 10 min. Photosynthetic electron transport appeared necessary for light activation of NR since activation was inhibited by the photosynthetic electron-transport inhibitor 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU), and, additionally, an electron acceptor (HCO 3 - ) was required. The PEPCase was also activated by light. However, this activation was not prevented by DCMU or lack of HCO 3 - . Loading of protoplasts in the dark with a weak acid resulted in activation of both NR and PEPCase. For NR, full activation was completed within 5 min, whereas for PEPCase a slower, modest activation continued for at least 40 min. Incubation of protoplasts with a weak base also gave activation of PEPCase, but not of NR. On the contrary, base loading counteracted light activation of NR. Since several treatments tested resulted in the modulation of either NR or PEPCase activity, but not both, signal transduction cascades leading to changes in activities appear to be very different for the two enzymes. Springer-Verlag, 1996 Acid loading nationallicence Hordeum nationallicence Light activation nationallicence Nitrate reductase nationallicence Phosphoenolpyruvate carboxylase nationallicence Protoplasts nationallicence DCMU : 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (diuron) nationallicence DMO : 5,5-dimethyl-2,4 oxazolidinedione nationallicence NR : nitrate reductase nationallicence PEPCase : Phosphoenolpyruvate carboxylase nationallicence Lillo Cathrine Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, G12 8QQ, Glasgow, UK aut Smith Lucy Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, G12 8QQ, Glasgow, UK aut Nimmo Hugh Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, G12 8QQ, Glasgow, UK aut Wilkins Malcolm Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, G12 8QQ, Glasgow, UK aut Planta Springer-Verlag 200/2(1996-10-01), 181-185 0032-0935 200:2<181 1996 200 425 https://doi.org/10.1007/BF00208307 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00208307 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Lillo Cathrine Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, G12 8QQ, Glasgow, UK aut NATIONALLICENCE 700 1- Smith Lucy Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, G12 8QQ, Glasgow, UK aut NATIONALLICENCE 700 1- Nimmo Hugh Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, G12 8QQ, Glasgow, UK aut NATIONALLICENCE 700 1- Wilkins Malcolm Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, G12 8QQ, Glasgow, UK aut NATIONALLICENCE 773 0- Planta Springer-Verlag 200/2(1996-10-01), 181-185 0032-0935 200:2<181 1996 200 425 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer