title: Molecular analysis of two hexokinase isoenzymes from Entamoeba histolytica.
abstract: The zymodemes, electrophoretic patterns of hexokinase, phosphoglucomutase and glucose phosphate isomerase isoenzymes, have been widely used to determine the pathogenicity of Entamoeba histolytica isolates. Although pathogenic and nonpathogenic forms of E. histolytica differ clearly in sequences of many homologous genes, a conversion between pathogenic and nonpathogenic zymodemes has been reported by several laboratories. To approach the question what might be the basis for the observed conversion, we examined the molecular biology of the hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) isoenzymes in pathogenic E. histolytica. We isolated two different cDNAs pHXK1 and pHXK2 coding for polypeptides with significant sequence similarity to hexokinases and deduced molecular masses of 49.8 kDa and 49.4 kDa. The two hexokinase sequences differed by 11% on the amino acid and by 8% on the nucleotide level. Expression of the cDNAs in Escherichia coli as nonfusion proteins gave two polypeptides with hexokinase activity. The recombinant Hxk1 and Hxk2 polypeptides comigrated with the more basic and more acidic isoforms of pathogenic amoebae in starch gel electrophoresis, as well as in low and high resolution isoelectric focussing gels. This identified the observed hexokinase isoenzymes of pathogenic E. histolytica as the products of two genes, hxk1 and hxk2.
authors.affiliation: Institute for Specific Prophylaxis and Tropical Medicine, Vienna, Austria.
authors.forename: S
authors.initials: S
authors.lastname: Ortner
authors.forename: B
authors.initials: B
authors.lastname: Plaimauer
authors.forename: M
authors.initials: M
authors.lastname: Binder
authors.forename: O
authors.initials: O
authors.lastname: Scheiner
authors.forename: G
authors.initials: G
authors.lastname: Wiedermann
authors.forename: M
authors.initials: M
authors.lastname: Duchêne
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics; D016054:DNA, Protozoan / Q000235:genetics; D004748:Entamoeba histolytica / Q000201:enzymology* / Q000235:genetics* / Q000472:pathogenicity; D004926:Escherichia coli / Q000235:genetics; D017125:Genes, Protozoan; D006593:Hexokinase / Q000235:genetics* / Q000302:isolation & purification; D007527:Isoenzymes / Q000235:genetics* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification; D013045:Species Specificity
chemical_list: D018076:DNA, Complementary; D016054:DNA, Protozoan; D007527:Isoenzymes; D011994:Recombinant Proteins; D006593:Hexokinase