Chloroplast and extrachloroplastic starch-degrading enzymes in Pisum sativum L. |
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Authors: | G Kakefuda S H Duke M S Hostak |
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Institution: | (1) Biology Department, University of Saskatchewan, S7N 0W0 Saskatoon, SK, Canada;(2) Crop Science Department, University of Guelph, N1G 2W1 Guelph, ONT, Canada |
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Abstract: | The organelles of soybean (Glycine max (L.) Merr.) protoplasts were separated using a recently developed procedure which allows rapid (3-h) recovery of a fraction enriched for coated vesicles (CVs). As determined by marker-enzyme enrichment and ultrastructural analysis of isolated membrane fractions, endoplasmic reticulum, Golgi membranes, glucan-synthase-II (EC 2.4.1.34)-containing membranes (putative plasma membrane), mitochondria, and CVs were enriched in separate fractions in a sucrose density gradient. Glucan synthase I (EC 2.4.1.12) had the highest specific activity in the Golgi-enriched and CV-enriched fractions and was found to comigrate with CVs upon rate-zonal centrifugation of a CV-enriched fraction. For further elucidation of the role of these latter organelles in cell-wall regeneration, freshly isolated protoplasts were pulsed with 3H]glucose for 20 min, and the disappearance of label from the organelles was followed for the ensuing 1 h. Although a CV-enriched fraction contained glucan synthase I, it contained very small amounts of labelled polysaccharide during the period of study. Pulse-chase experiments with 3H]glucose helped to confirm the role of the Golgi apparatus in secretion of matrix polysaccharides by protoplasts.Abbreviations CV(s)
coated vesicle(s)
- Da
dalton
- ER
endoplasmic reticulum
- GSI,II
glucan synthase I and II, respecitively
Two whom correspondence should be directed. Address after February 1986:Department of Biology, Texas A&M University. College Station, TX 77843-3258, USA |
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Keywords: | Exocytosis Glycine (cell fractionation) Golgi apparatus Protoplast (cell-wall regeneration) Secretion Vesicle (coated) |
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