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Substrate specificity and product inhibition of different forms of fructokinases and hexokinases in developing potato tubers

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The substrate dependence and product inhibition of three different fructokinases and three different hexokinases from growing potato (Solanum tuberosum L.) tubers was investigated. The tubers contained three specific fructokinases (FK1, FK2, FK3) which had a high affinity for fructose K m=64, 90 and 100 (μM) and effectively no activity with glucose or other hexose sugars. The affinity for ATP (K m=26, 25 and 240 μM) was at least tenfold higher than for other nucleoside triphosphates. All three fructokinases showed product inhibition by high fructose (K i=5.7, 6.0 and 21 mM) and were also inhibited by ADP competitively to ATP. Sensitivity to ADP was increased in the presence of high fructose, or fructose-6-phosphate. In certain conditions, the K i (ADP) was about threefold below the K m (ATP). All three fructokinase were also inhibited by fructose-6-phosphate acting non-competitively to fructose (K i=1.3 mM for FK2). FK1 and FK2 showed very similar kinetic properties whereas FK3, which is only present at low activities in the tuber but high activities in the leaf, had a generally lower affinity for ATP, and lower sensitivity to inhibition by ADP and fructose. The tuber also contained three hexokinases (HK1, HK2, HK3) which had a high affinity for glucose (K m=41, 130 and 35 μM) and mannose but a poor affinity for fructose (K m=11, 22 and 9 mM). All three hexokinases had a tenfold higher affinity for ATP (K m=90, 280 and 560 μM) than for other nucleoside triphosphates. HK1 and HK2 were both inhibited by ADP (K i=40 and 108 μM) acting competitively to ATP. HK1, but not HK2, was inhibited by glucose-6-phosphate, which acted non-competitively to glucose (K i=4.1 mM). HK1 and HK2 differed, in that HK1 had a narrower pH optimum, a higher affinity for its substrate, and showed inhibition by glucose-6-phosphate. The relevance of these properties for the regulation of hexose metabolism in vivo is discussed.

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nucleoside triphosphate

Pi :

inorganic phosphate




  1. Baldus, B., Kelly, G.J., Latzko, E. (1981) Hexokinases of spinach leaves. Phytochemistry 20, 1811–1814

  2. Baysdorfer, C., Kremer, D.F., Sicher, R.C. (1989) Partial purification and characterization of fructokinase activity from barley leaves. J. Plant Physiol. 134, 156–161

  3. Copeland, L., Turner, J.F. (1987) In: The biochemistry of plants, vol. 11, pp. 107–128, Stumpf, P.K., Conn, E.E., eds. Academic Press, San Diego

  4. Copeland, L., Tanner, G.J. (1988) Hexose kinases of avocado. Physiol. Plant. 74, 531–536

  5. Copeland, L., Harrison, D.D., Turner, J.F. (1978) Fructokinase (fraction III) of pea seeds. Plant Physiol. 62, 291–294

  6. Copeland, L., Stone, S.R., Turner, J.F. (1984) Kinetic studies of fructokinase I of pea seeds. Arch. Biochem. Biophys. 233, 748–760

  7. Dancer, J., Neuhaus, H.E., Stitt, M. (1990a) Subcellular compartmentation of uridine nucleotides and nucleoside-5′-diphosphate kinase in leaves. Plant Physiol. 92, 637–641

  8. Dancer, J., Hatzfeld, W.-D., Stitt, M. (1990b) Cytosolic cycles regulate the turnover of sucrose in heterotrophic cell-suspension cultures of Chenopodium rubrum L. Planta 182, 223–231

  9. Doehlert, D.C. (1989) Separation and characterization of four hexose kinases from developing maize kernels. Plant Physiol. 89, 1042–1048

  10. Doehlert, D.C. (1990) Fructokinases from developing maize kernels differ in their specificity for nucleoside triphosphates. Plant Physiol. 93, 353–355

  11. Geigenberger, P., Stitt, M. (1991) A “futile” cycle of sucrose synthesis and degradation is involved in regulating partitioning between sucrose, starch and respiration in cotyledons of germinating Ricinus communis L. seedlings when phloem transport is inhibited. Planta 185, 81–90

  12. Geigenberger, P., Stitt, M. (1993) Sucrose synthase catalyses a readily reversible reaction in potato tubers and other plant tissues. Planta 189, 329–339

  13. Gerhardt, R., Stitt, M., Heldt, H.W. (1987) Subcellular metabolite levels in spinach leaves. Regulation of sucrose synthesis during diurnal alterations in photosynthetic partitioning. Plant Physiol. 83, 399–407

  14. Hajirezaei, M., Stitt, M. (1991) Contrasting roles for pyrophosphate:fructose-6-phosphate phosphotransferase during aging of tissue slices from potato tubers and carrot storage tissues. Plant Sci. 77, 177–183

  15. Heineke, D., Sonnewald, U., Büssis, D., Gunter, G., Leidreiter, K., Wilke, I., Raschke, K., Willmitzer, L., Heldt, H.W. (1992) Apoplastic expression of yeast-derived invertase in potato. Effects on photosynthesis, leaf solute composition, water relations, and tuber composition. Plant Physiol. 100, 301–308

  16. Higgins, T.J.C., Easterby, J.S. (1974) Wheatgerm hexokinase: physical and active-site properties. Eur. J. Biochem. 45, 147–160

  17. Huber, S.C., Akazawa, T. (1986) A novel sucrose synthase pathway for sucrose degradation in cultured sycamore cells. Plant Physiol. 81, 1008–1013

  18. Jelitto, T., Sonnewald, U., Willmitzer, L., Hajirezaei, M., Stitt, M. (1992) Inorganic pyrophosphate content and metabolites in potato and tobacco plants expressing E. coli pyrophosphatase in their cytosol. Planta 188, 238–244

  19. Kruger, N.J. (1990) Carbohydrate synthesis and degradation. In: Plant physiology, biochemistry and molecular biology, pp. 59–76, Dennis, D.T., Turpin, D.M., eds. Longman, Harlow

  20. Miernyk, J.A., Dennis, D.T. (1983) Mitochondrial, plastid, and cytosolic isozymes of hexokinase from developing endosperm of Ricinus communis. Arch. Biochem. Biophys. 226, 458–468

  21. Morrell, S., ap Rees, T. (1986) Sugar metabolism in developing tubers of Solanum tuberosum. Phytochemistry 25, 1579–1585

  22. Newsholme, E.A., Robinson, J., Taylor, K. (1967) A radiochemical enzymatic activity assay for glycerol kinase and hexokinase. Biochim. Biophys. Acta 132, 338–346

  23. Niemeyer, H., Cerpa, C., Rabajille, E. (1987) Inhibition of hexokinase activity by a fructose-2,6-bisphosphate-dependent cytosolic protein from liver. Arch. Biochem. Biophys. 257, 17–26

  24. Quick, P., Siegl, G., Neuhaus, E., Feil, R., Stitt, M. (1989) Short-term water stress leads to a stimulation of sucrose synthesis by activating sucrose-phosphate synthase. Planta 177, 535–546

  25. Renz, A., Merlo, L., Stitt, M. (1993) Partial purification from potato tubers of three fructokinases and three hexokinases which show differing organ and developmental specificity. Planta 190, 156–165

  26. Schnarrenberger, C. (1990) Characterization and compartmentation, in green leaves, of hexokinases with different specificities for glucose, fructose, and mannose and for nucleoside triphosphates. Planta 181, 249–255

  27. Sonnewald, U., Brauer, M., von Schaewen, A., Stitt, M., Willmitzer, L. (1991) Transgenic tobacco plants expressing yeast-derived invertase in either the cytosol, vacuole or apoplast: a powerful tool for studying sucrose metabolism and sink/source interactions. Plant J. 1, 95–106

  28. Stitt, M., Lilley, R.McC., Heldt, H.W. (1982) Adenine nucleotide levels in the cytosol, chloroplasts and mitochondria of wheat leaf protoplasts. Plant Physiol. 70, 971–977

  29. Turner, J.F., Turner, D.H. (1980) The regulation of glycolysis and the pentose phosphate pathway. In: The biochemistry of plants, vol. 2, pp. 279–316, Stumpf, P.K., Conn, E.E., eds. Academic Press, New York

  30. Turner, J.F., Copeland, L. (1981) Hexokinase II of pea seeds. Plant Physiol. 68, 1123–1127

  31. Turner, J.F., Chensee, Q.J., Harrison, D.D. (1977a) Glucokinase of pea seeds. Biochim. Biophys. Acta 480, 367–375

  32. Turner, J.F., Harrison, D.D., Copeland, L. (1977b) Fructokinase (fraction IV) of pea seeds. Plant Physiol. 60, 666–669

  33. Wagner, K.G., Backer, A.I. (1992) Dynamics of nucleotides in plants studied on a cellular basis. Int. Rev. Cytology 134, 1–84

  34. Walker, D.G. (1966) The nature and function of hexokinases in animal tissues. Essays Biochem. 2, 33–67

  35. Xu, D.-P., Sung, S.-J.S., Loboda, T., Kormanik, P.P., Black, C.C. (1989) Characterization of sucrolysis via the uridine diphosphate and pyrophosphate-dependent sucrose synthase pathway. Plant Physiol. 90, 635–642

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Correspondence to Mark Stitt.

Additional information

This work was supported by the Deutsche Froschungsgemeinschaft (SFB 137). We are grateful to Professor E. Beck (Lehrstuhl für Pflanzenphysiologie, Universität Bayreuth, FRG) for providing laboratory facilities.

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Renz, A., Stitt, M. Substrate specificity and product inhibition of different forms of fructokinases and hexokinases in developing potato tubers. Planta 190, 166–175 (1993).

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Key words

  • Fructokinase
  • Hexokinase
  • Solanum
  • Sucrose metabolism