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Biologia Plantarum

, Volume 30, Issue 4, pp 275–284 | Cite as

Hexokinases of tobacco leaves: Subcellular localization and characterization

  • Milada ŠindelÁŘovÂ
  • L. ŠindelÂr
Original paper

Abstract

Subeellular localization of the enzymes which phosphorylate hexoses was studied in photosynthesizing tobacco leaves by means of differential centrifugation and centrifugation in sucrose gradient. More than 80 % of the total hexokinase activity of leaf tissues were found to be associated with the particulate fraction of mitochondria; however, the ratio of the particulate hexokinase fraction to the soluble fraction was influenced by the extraction medium applied. The particulate hexokinases showed a high affinity to glucose (Km = 26.8 μM) and a relatively low affinity to fructose (Km = 17.6 mM). They had a broad pH optimum, because 81 % of the phosphorylating activity obtained for glucose and 75 % of the activity obtained for fructose occurred in pH range from 7.9 to 9.1 (Tris-HCl buffer). The hexokinases were Mg2+ dependent with the highest activity occurring at equimolar Mg2+ and ATP concentrations. Their activity was enhanced by KC1, NaCl, and (NH4)2SO4 at 30 to 120 mM concentrations.

Keywords

Fructose Subcellular Localization Hexokinase Sucrose Gradient Tobacco Leave 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Academia 1988

Authors and Affiliations

  • Milada ŠindelÁŘovÂ
    • 1
  • L. ŠindelÂr
    • 1
  1. 1.Institute of Experimental BotanyCzechoslovak Academy of SciencesCzechoslovakia

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