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Gene Review

HXK2  -  hexokinase 2

Saccharomyces cerevisiae S288c

Synonyms: HEX1, HKB, Hexokinase PII, Hexokinase-2, Hexokinase-B, ...
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High impact information on HXK2

  • Deletion of HEX1 in N. crassa eliminates Woronin bodies from the cytoplasm and results in hyphae that exhibit a cytoplasmic-bleeding phenotype in response to cell lysis [1].
  • Here we purify the Woronin body from Neurospora crassa and isolate Hex1, a new protein containing a consensus sequence known as peroxisome-targeting signal-1 (PTS1) [1].
  • We show that Hex1 is localized to the matrix of the Woronin body by immunoelectron microscopy, and that a green fluorescent protein- (GFP-)Hex1 fusion protein is targeted to yeast peroxisomes in a PTS1- and peroxin-dependent manner [1].
  • In contrast, expression of LexA-Reg1p containing mutations at phenylalanine in the putative PP-1C-binding site motif (K/R)(X)(I/V)XF was unable to rescue Hxk2p dephosphorylation in intact yeast or restore Hxk2p phosphatase activity [2].
  • Mixed peptide sequencing identified these proteins as hexokinase II (Hxk2p) and the E1alpha subunit of pyruvate dehydrogenase [2].

Biological context of HXK2


Anatomical context of HXK2


Associations of HXK2 with chemical compounds


Physical interactions of HXK2

  • Mediator factor Med8p interacts with the hexokinase 2: implication in the glucose signalling pathway of Saccharomyces cerevisiae [13].
  • We conclude that Hxk2 operates by interacting with Mig1 to generate a repressor complex located in the nucleus of S. cerevisiae during growth in glucose medium [11].
  • Furthermore, we demonstrate using gel mobility shift analysis that Hxk2 participates in DNA-protein complexes with cis-acting regulatory elements of the SUC2 gene promoter [14].
  • The surface area of the hexokinase A-glucose complex exposed to solvent is smaller than that of native hexokinase B [15].

Enzymatic interactions of HXK2


Regulatory relationships of HXK2

  • Using the set of six hxk2 mutants it was shown that there is a good correlation between the glucose-induced cAMP signal and in vivo hexokinase activity [5].
  • Rgt1 represses HXK2 expression by binding specifically to the motif (CGGAAAA) located at -395 bp relative to the ATG translation start codon in the HXK2 promoter [17].
  • Here we report that Hxk2 has a glucose-regulated nuclear localization and that Mig1, a transcriptional repressor responsible for glucose repression of many genes, is required to sequester Hxk2 into the nucleus [11].
  • Tpk3 and Snf1 protein kinases regulate Rgt1 association with Saccharomyces cerevisiae HXK2 promoter [18].
  • An hxk2-delta 1::URA3 mutant did not detectably express Hxt2p in ethanol or galactose, but an ssn6-delta9 mutant did highly express Hxt2p in both carbon sources [19].

Other interactions of HXK2

  • The hxk2 single mutant, as well as the double mutant, failed to show catabolite repression in all three systems, while the hxk1 null mutation had little or no effect on catabolite repression [20].
  • Components of the glucose repression pathway (Hxk2p and Reg1p) are also required for generation of the high-level glucose induction signal for expression of the HXT1 gene [21].
  • We conclude that Hxk2p operates through the MED8 site, by interacting with Med8p, in the glucose signal transduction pathway of Saccharomyces cerevisiae [13].
  • The expression of CAT8-lacZ and SIP4-lacZ has been also measured in mig1, tup1 or hxk2 mutants, partially refractory to catabolite repression [22].
  • The glucose inhibition pathway requires HXK2, REG1, and GSF1 and appears to overlap upstream with the glucose repression pathway [23].

Analytical, diagnostic and therapeutic context of HXK2


  1. A new self-assembled peroxisomal vesicle required for efficient resealing of the plasma membrane. Jedd, G., Chua, N.H. Nat. Cell Biol. (2000) [Pubmed]
  2. Reg1p targets protein phosphatase 1 to dephosphorylate hexokinase II in Saccharomyces cerevisiae: characterizing the effects of a phosphatase subunit on the yeast proteome. Alms, G.R., Sanz, P., Carlson, M., Haystead, T.A. EMBO J. (1999) [Pubmed]
  3. Carbon source-dependent phosphorylation of hexokinase PII and its role in the glucose-signaling response in yeast. Randez-Gil, F., Sanz, P., Entian, K.D., Prieto, J.A. Mol. Cell. Biol. (1998) [Pubmed]
  4. Phenotypic characterization of glucose repression mutants of Saccharomyces cerevisiae using experiments with 13C-labelled glucose. Raghevendran, V., Gombert, A.K., Christensen, B., Kötter, P., Nielsen, J. Yeast (2004) [Pubmed]
  5. Novel alleles of yeast hexokinase PII with distinct effects on catalytic activity and catabolite repression of SUC2. Hohmann, S., Winderickx, J., de Winde, J.H., Valckx, D., Cobbaert, P., Luyten, K., de Meirsman, C., Ramos, J., Thevelein, J.M. Microbiology (Reading, Engl.) (1999) [Pubmed]
  6. The hexokinase isoenzyme PII of Saccharomyces cerevisiae ia a protein kinase. Herrero, P., Fernández, R., Moreno, F. J. Gen. Microbiol. (1989) [Pubmed]
  7. Identification and characterisation of two transcriptional repressor elements within the coding sequence of the Saccharomyces cerevisiae HXK2 gene. Herrero, P., Ramírez, M., Martínez-Campa, C., Moreno, F. Nucleic Acids Res. (1996) [Pubmed]
  8. Candida albicans HEX1 gene, a reporter of gene expression in Saccharomyces cerevisiae. Niimi, K., Shepherd, M.G., Cannon, R.D. Arch. Microbiol. (1998) [Pubmed]
  9. Saccharomyces cerevisiae null mutants in glucose phosphorylation: metabolism and invertase expression. Walsh, R.B., Clifton, D., Horak, J., Fraenkel, D.G. Genetics (1991) [Pubmed]
  10. The growth and signalling defects of the ggs1 (fdp1/byp1) deletion mutant on glucose are suppressed by a deletion of the gene encoding hexokinase PII. Hohmann, S., Neves, M.J., de Koning, W., Alijo, R., Ramos, J., Thevelein, J.M. Curr. Genet. (1993) [Pubmed]
  11. The glucose-regulated nuclear localization of hexokinase 2 in Saccharomyces cerevisiae is Mig1-dependent. Ahuatzi, D., Herrero, P., de la Cera, T., Moreno, F. J. Biol. Chem. (2004) [Pubmed]
  12. Schizosaccharomyces pombe possesses an unusual and a conventional hexokinase: biochemical and molecular characterization of both hexokinases. Petit, T., Blázquez, M.A., Gancedo, C. FEBS Lett. (1996) [Pubmed]
  13. Mediator factor Med8p interacts with the hexokinase 2: implication in the glucose signalling pathway of Saccharomyces cerevisiae. de la Cera, T., Herrero, P., Moreno-Herrero, F., Chaves, R.S., Moreno, F. J. Mol. Biol. (2002) [Pubmed]
  14. The hexokinase 2 protein participates in regulatory DNA-protein complexes necessary for glucose repression of the SUC2 gene in Saccharomyces cerevisiae. Herrero, P., Martínez-Campa, C., Moreno, F. FEBS Lett. (1998) [Pubmed]
  15. Glucose-induced conformational change in yeast hexokinase. Bennett, W.S., Steitz, T.A. Proc. Natl. Acad. Sci. U.S.A. (1978) [Pubmed]
  16. Glycolytic enzymes and intermediates in carbon catabolite repression mutants of Saccharomyces cerevisiae. Entian, K.D., Zimmermann, F.K. Mol. Gen. Genet. (1980) [Pubmed]
  17. Rgt1, a glucose sensing transcription factor, is required for transcriptional repression of the HXK2 gene in Saccharomyces cerevisiae. Palomino, A., Herrero, P., Moreno, F. Biochem. J. (2005) [Pubmed]
  18. Tpk3 and Snf1 protein kinases regulate Rgt1 association with Saccharomyces cerevisiae HXK2 promoter. Palomino, A., Herrero, P., Moreno, F. Nucleic Acids Res. (2006) [Pubmed]
  19. Expression of high-affinity glucose transport protein Hxt2p of Saccharomyces cerevisiae is both repressed and induced by glucose and appears to be regulated posttranslationally. Wendell, D.L., Bisson, L.F. J. Bacteriol. (1994) [Pubmed]
  20. Effects of null mutations in the hexokinase genes of Saccharomyces cerevisiae on catabolite repression. Ma, H., Botstein, D. Mol. Cell. Biol. (1986) [Pubmed]
  21. Three different regulatory mechanisms enable yeast hexose transporter (HXT) genes to be induced by different levels of glucose. Ozcan, S., Johnston, M. Mol. Cell. Biol. (1995) [Pubmed]
  22. Regulatory elements in the FBP1 promoter respond differently to glucose-dependent signals in Saccharomyces cerevisiae. Zaragoza, O., Vincent, O., Gancedo, J.M. Biochem. J. (2001) [Pubmed]
  23. Analysis of the mechanism by which glucose inhibits maltose induction of MAL gene expression in Saccharomyces. Hu, Z., Yue, Y., Jiang, H., Zhang, B., Sherwood, P.W., Michels, C.A. Genetics (2000) [Pubmed]
  24. Analysis by atomic force microscopy of Med8 binding to cis-acting regulatory elements of the SUC2 and HXK2 genes of saccharomyces cerevisiae. Moreno-Herrero, F., Herrero, P., Colchero, J., Baró, A.M., Moreno, F. FEBS Lett. (1999) [Pubmed]
  25. Calorimetric determination of thermodynamic parameters of reaction reveals different enthalpic compensations of the yeast hexokinase isozymes. Bianconi, M.L. J. Biol. Chem. (2003) [Pubmed]
  26. Sequencing a protein by x-ray crystallography. I. Interpretation of yeast hexokinase B at 2.5 A resolution by model building. Anderson, C.M., McDonald, R.C., Steitz, T.A. J. Mol. Biol. (1978) [Pubmed]
  27. Structure-function analysis of yeast hexokinase: structural requirements for triggering cAMP signalling and catabolite repression. Kraakman, L.S., Winderickx, J., Thevelein, J.M., De Winde, J.H. Biochem. J. (1999) [Pubmed]
  28. Volumetric and spectroscopic characterizations of glucose-hexokinase association. Filfil, R., Chalikian, T.V. FEBS Lett. (2003) [Pubmed]
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