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Characterization of Starch-Debranching Enzymes in Pea Embryos1
Shanghai Institute of Plant Physiology, 300 Fonglin Road, Shanghai, China 200032 (Z.-P.Z.); and John Innes Centre, Colney Lane, Norwich NR4 7UH, United Kingdom (C.M.H., U.R., A.M.S.) Two distinct types of debranching enzymes have been identified in developing pea (Pisum sativum L.) embryos using native gel analysis and tests of substrate preference on purified or partially purified activities. An isoamylase-like activity capable of hydrolyzing amylopectin and glycogen but not pullulan is present throughout development and is largely or entirely confined to the plastid. Activities capable of hydrolyzing pullulan are present both inside and outside of the plastid, and extraplastidial activity increases relative to the plastidial activity during development. Both types of debranching enzyme are also present in germinating embryos. We argue that debranching enzymes are likely to have a role in starch metabolism in the plastid of the developing embryo and in starch degradation during germination. 1 This research was supported by a competitive strategic grant from the Biotechnology and Biological Sciences Research Council (UK) to the John Innes Centre, by an International Collaboration Project funded by the European Union (contract no. CI1*/0417/00), by funding from the Chinese National Natural Foundation of Science to Z.-P.Z., and by an Erasmus Award (European Union) to U.R. 2 Present address: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Karl-Liebknecht Strasse 25, 14476 Golm, Germany. * Corresponding author; e-mail smitha{at}bbsrc.ac.uk; fax 44-1603-456844.
Plant Physiol. (1998) 118: 581-590
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