Poster Abstract
Cells of the golden-brown alga P. malhamensis regain their volume after osmotic shrinkage mainly by production of isofloridoside (IF, a-galactosyl-1→-1-glycerol)1. A few min after shrinkage a soluble key enzyme of the relevant pathway, the UDP-Gal:α-glycerol-3-phosphate lα-galactosyl- transferase has gained activity. This increase parallels the degree of shrinkage and also disappears shortly after an artificial swelling, indicating a physiological role of the activation process. Evidence is accumulating that this is due to a cascade of proteolytic events, which can be induced in homogenates from cells of standard volume by Ca2+. The proteinase responsible for activating the galactosyltransferase has been purified recently and its involvement in the regulation process demonstrated2. The overall sequence of events appears to be clear for the right-hand part, but hypothetical for the membrane-part of the following scheme:
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References
H. Kauss, Volume regulation in Poterioochromonas. Involvement of calmodulin in the Ca2+ stimulated activation of isofloridoside- phosphate synthase, Plant Physiol. 71: 169 (1983).
D. Kohle and H. Kauss, Purification of a membrane-derived proteinase capable of activating a galactosyltransferase involved in volume regulation, Biochim. Biophys. Acta 799: 59 (1984).
H. Kauss, Volume regulation: Activation of a membrane-associated cryptic enzyme system by detergent-like action of phenothiazine drugs, Plant Sci. Lett. 26: 103 (1982).
H. Kauss, A membrane-derived proteinase capable of activating a galactosyl-transferase involved in volume regulation of Poterioochromonas, in: “Plant Proteolytic Enzymes,” M. J. Dalling, ed., CRC Press, Boca Raton (1985).
H. Kauss and U. Rausch, Compartmentation of Ca and its possible role in volume regulation of Poterioochromonas, in.: ‘Compartments in Algal Cells and their Interaction,’ W. Wiessner, D. Robinson, and R. C. Starr, ed., Springer-Verlag, Berlin Heidelberg (1984).
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© 1986 Plenum Press, New York
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Kauss, H. (1986). Ca2+-Dependent Generation of a Membrane-Borne Proteinase Involved in Volume Regulation of Poterioochromonas . In: Trewavas, A.J. (eds) Molecular and Cellular Aspects of Calcium in Plant Development. NATO ASI Series, vol 104. Springer, Boston, MA. https://doi.org/10.1007/978-1-4613-2177-4_61
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DOI: https://doi.org/10.1007/978-1-4613-2177-4_61
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