title: The binding of glucose to yeast hexokinase monomers is independent of ionic strength.
abstract: Hoggett & Kellett [Eur. J. Biochem. 66, 65-77 (1976)] have reported that the binding of glucose to the monomer of hexokinase PII isoenzyme is independent of ionic strength, in contrast to the subsequent claim of Feldman & Kramp [Biochemistry 17, 1541-1547 (1978)] that the binding is strongly dependent on ionic strength. Since measurements with native hexokinase P forms are complicated by the fact that the enzyme exists in a monomer-dimer association-dissociation equilibrium, we have now studied the binding of glucose to the proteolytically-modified S forms which are monomeric. At pH 8.5, the affinity of glucose for both SI and SII monomers is independent of salt concentration over the range of KCl concentrations 0-1.0 mol . dm-3 and is in good agreement with that of the corresponding P forms in both low and high salt. These observations confirm that the binding of glucose to hexokinase P monomers is independent of ionic strength and that the affinity of glucose for the hexokinase PII monomer is about an order of magnitude greater than that for the dimer.
mesh_terms: D001665:Binding Sites; D005947:Glucose / Q000378:metabolism*; D006593:Hexokinase / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism*; D046911:Macromolecular Substances; D009994:Osmolar Concentration; D011189:Potassium Chloride / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013050:Spectrometry, Fluorescence
chemical_list: D007527:Isoenzymes; D046911:Macromolecular Substances; D011189:Potassium Chloride; D006593:Hexokinase; D005947:Glucose