This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (41) Citing Articles via Google Scholar Google Scholar Articles by Kreimer, G. Articles by Latzko, E. Search for Related Content PubMed PubMed Citation Articles by Kreimer, G. Articles by Latzko, E. Agricola Articles by Kreimer, G. Articles by Latzko, E.

Metabolism and Enzymology

Stromal Free Calcium Concentration and Light-Mediated Activation of Chloroplast Fructose-1,6-Bisphosphatase ¹

Botanisches Institut der Westfälischen Wilhelms-Universität, D-4400 Münster, Schlossgarten 3, Federal Republic of Germany

Light-mediated activation of fructose-1,6-bisphosphatase (EC 3.1.3.11) in intact spinach chloroplasts (Spinacia oleracea L.) is enhanced in the presence of 10^–5 molar external free Ca²⁺. The most pronounced effect is observed during the first minutes of illumination. Ruthenium red, an inhibitor of light-induced Ca²⁺ influx, inhibits this Ca²⁺ stimulated activation. In isolated stromal preparations, the activation of fructose-1,6-bisphosphatase is already enhanced by 2 minutes of exposure to elevated Ca²⁺ concentrations in the presence of physiological concentrations of Mg²⁺ and fructose-1,6-bisphosphate. Maximal activation of the enzyme is achieved between 0.34 and 0.51 millimolar Ca²⁺. The Ca²⁺ mediated activation decreases with increasing fructose-1,6-bisphosphate concentration and with increasing pH. The data are consistent with the proposal that the illumination of chloroplasts leads to a transient increase of free stromal Ca²⁺. In dark-kept chloroplasts the steady-state concentration of free stromal Ca²⁺ is 2.4 to 6.3 micromolar as determined by null point titration. These observations support our previous proposal that light-induced Ca²⁺ influx into chloroplasts does not only influence the cytosolic concentration of free Ca²⁺ but also regulates enzymatic processes inside the chloroplast.

This article has been cited by other articles:

				K. Ifuku, Y. Yamamoto, T.-a. Ono, S. Ishihara, and F. Sato PsbP Protein, But Not PsbQ Protein, Is Essential for the Regulation and Stabilization of Photosystem II in Higher Plants Plant Physiology, November 1, 2005; 139(3): 1175 - 1184. [Abstract] [Full Text] [PDF]

				J. Sai and C. H. Johnson Dark-Stimulated Calcium Ion Fluxes in the Chloroplast Stroma and Cytosol PLANT CELL, June 1, 2002; 14(6): 1279 - 1291. [Abstract] [Full Text] [PDF]

				M. Tazawa, M. Kikuyama, and Y. Okazaki Different Cytoplasmic Calcium Contents Among Three Species of Characeae Plant Cell Physiol., June 1, 2001; 42(6): 620 - 626. [Abstract] [Full Text] [PDF]

				W. F. Ettinger, A. M. Clear, K. J. Fanning, and M. Lou Peck Identification of a Ca2+/H+ Antiport in the Plant Chloroplast Thylakoid Membrane Plant Physiology, April 1, 1999; 119(4): 1379 - 1386. [Abstract] [Full Text]

				M. H. Roh, R. Shingles, M. J. Cleveland, and R. E. McCarty Direct Measurement of Calcium Transport across Chloroplast Inner-Envelope Vesicles Plant Physiology, December 1, 1998; 118(4): 1447 - 1454. [Abstract] [Full Text]