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Sucrose synthase isoforms in cultured tobacco cells

Publiceringsår: 2004
Språk: Engelska
Sidor: 299-306
Publikation/Tidskrift/Serie: Plant Physiology and Biochemistry
Volym: 42
Nummer: 4
Dokumenttyp: Artikel
Förlag: Elsevier

Sammanfattning

The plant enzyme sucrose synthase (SuSy; EC 2.4.1.13) catalyzes the reversible conversion of sucrose and UDP into UDP-glucose (UDP-Glc) and fructose. The enzyme exists in different isoforms and is both located in the cytosol, membrane-bound and associated to the actin cytoskeleton. We here investigate sucrose synthase from tobacco (Nicotiana tabacum L.) BY-2 heterotrophic cell suspensions. Two different isoforms of sucrose synthase SuSy1 and SuSy2, could be purified from cytosolic extracts of these cells using a combination of poly(ethylene glycol) (PEG) precipitation, gel filtration, ion-exchange chromatography and affinity chromatography. They were clearly distinct. both with regard to the binding to the ion-exchange column and with regard to their kinetic and regulatory properties. SuSy 1, the more abundant species, showed lower V-max and K-m for sucrose and UDP compared to the less abundant SuSy2. The activity of SuSy2 in the breakdown direction was stimulated by 60% by actin, in contrast to that of SuSy 1, which showed a 17% inhibition. An indication of interaction between SuSy I and actin was obtained by partitioning in aqueous Dextran-PEG two-phase systems. Furthermore, fructose 2,6-bisphosphate (F26BP) at micromolar concentrations stimulated SuSy2 in the presence of actin while SuSy I was strongly inhibited by fructose. Possible roles of these two isoforms in the sucrose turnover in BY-2 cells are discussed. (C) 2004 Elsevier SAS. All rights reserved.

Disputation

Nyckelord

  • Chemistry
  • Two-phase partitioning
  • Tobacco
  • Sucrose synthase
  • Sucrolysis
  • 6-bisphosphate
  • Fructose 2
  • Actin
  • BY-2 cells

Övriga

Published
Yes
  • ISSN: 0981-9428

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