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


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.


Fructose Subcellular Localization Hexokinase Sucrose Gradient Tobacco Leave 
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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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