Calcium ions and polyamines activate the plasma membrane-located 1,3-β-glucan synthase.
Sucrose-density-gradient centrifugation and partitioning in a polyethylene glycol/dextran two-phase system were used to isolate plasmamembrane vesicles from microsomal preparations of soybean cell suspension cultures. Both methods resulted in the enrichment of the activity of a 1,3-β-glucan synthase which forms a polymer consisting of more than 99% of 1,3-linked glucose (callose). Digitonin increases the 1,3-β-glucan synthase activity in the various membrane fractions to a different degree, supporting the suggestion that this enzyme is vectorially arranged in the plasma membrane. The enzyme is greatly activated either by poly-L-ornithine or synergistically by Ca(2+) and spermine, indicating that the same enzyme is affected and exhibits the regulatory properties necessary for callose synthesis.
Fachbereich Biologie, Universität Kaiserslautern, Postfach 3049, D-6750, Kaiserslautern, Federal Republic of Germany.
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J
Fink
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Jeblick
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W
Blaschek
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Kauss