Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.1.1 (hexokinase)
 5,274 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Entamoeba histolytica and Entamoeba dispar have only recently been defined as two separate species. E. histolytica, the pathogenic species, is the microorganism causing invasive intestinal amoebiasis and/or liver abscess, while the morphologically similar E. dispar is nonpathogenic and noninvasive. The gold standard for the distinction of the two species has been the isoenzyme electrophoresis of phosphoglucomutases (EC 5.4.2.2) and hexokinases (EC 2.7.1.1), but there had also been a controversy about the possibility of a conversion of isoenzyme patterns. In this study, we cloned the phosphoglucomutase (PGM) cDNAs from the pathogenic and the nonpathogenic species. The deduced amino acid sequences were only 2.4% different. The cDNAs were expressed in Escherichia coli under the control of a T7 RNA polymerase promoter. The recombinant polypeptides displayed strong phosphoglucomutase activity, each of the recombinant enzymes comigrated with its natural counterpart from E. histolytica and E. dispar in the starch gel electrophoresis. Our results give a biochemical interpretation of the PGM isoenzyme pattern and support the clear distinction between the two species.
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PMID:Molecular and biochemical characterization of phosphoglucomutases from Entamoeba histolytica and Entamoeba dispar. 949 37

Entamoeba histolytica is responsible for amoebic colitis and liver abscess in humans. Entamoeba dispar is a closely related, morphologically indistinguishable nonpathogenic species. The hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) isoenzyme patterns distinguish the pathogenic and nonpathogenic species. Both species possess two hexokinases with very similar molecular mass and different isoelectric points. In order to understand the role of the two different isoenzymes from E. histolytica, we purified the recombinant hexokinases HXK1 and HXK2 and examined substrate spectrum and kinetic properties. The two enzymes displayed similar temperature and pH optima, they were inhibited strongly by AMP and ADP, not by glucose 6-phosphate. Both enzymes phosphorylated glucose well and were unable to phosphorylate fructose or galactose. We also detected significant differences. HXK1 was more sensitive to inhibition by AMP and ADP. Mannose was phosphorylated well by HXK1, but at a much lower rate by HXK2. We attempted to expand the substrate spectrum of E. histolytica HXK1 by modifying its active site to become similar to the active site of the fructose phosphorylating yeast hexokinase PII. None of the nine mutants gained any fructokinase activity, but all of them retained at least some glucokinase and mannokinase activity. Mannokinase activity was decreased drastically by two single amino acid exchanges, both of which contributed significantly to this effect. The data indicate that a complex interaction of a number of amino acid residues is necessary for the ability to phosphorylate a given hexose.
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PMID:Differences in substrate specificity and kinetic properties of the recombinant hexokinases HXK1 and HXK2 from Entamoeba histolytica. 1061

Information on the effect of parasitic infections on lipid parameters is scarce. Certain parasites induce significant changes in lipid parameters, as demonstrated by the fact that substitution of lipid/cholesterol for serum in axenic culture medium (in vitro) and in experimental models (in vivo) supports vigorous growth of Entamoeba histolytica. Thus, significant changes in lipid parameters may be induced in an infected host. Blood samples are obtained from intestinal amoebiasis patients passing E. histolytica (n=8), E. dispar (n=15) or Giardia lamblia (n=9) cysts, or diagnosed with amoebic liver abscess (ALA; n=50) and from apparently normal healthy individuals (control group; n=30). Levels of total serum cholesterol, high-density lipoprotein and low-density lipoprotein are assessed using commercial kits. E. histolytica and E. dispar isolates are differentiated by hexokinase isoenzyme electrophoresis and by enzyme-linked immunosorbent assay (ELISA; Techlab) tests. Results show that E. histolytica, E. dispar and G. lamblia cyst passers had significantly lower levels of total serum cholesterol (73.42 +/- 2.24 mg/dL), compared to levels in ALA cases (101 +/- 2.85 mg/dL) and in controls (166.26 +/- 2.02 mg/dL). Further study of a greater number of cases is needed to explore the relevance of this finding.
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PMID:Altered lipid parameters in patients infected with Entamoeba histolytica, Entamoeba dispar and Giardia lamblia. 1599 78

We have recently proposed revival of the name Entamoeba nuttalli Castellani, 1908 for a virulent amoeba (P19-061405 strain) isolated from a rhesus monkey (Macaca mulatta) and located phylogenetically between E. histolytica and E. dispar. In this study, E. nuttalli was isolated from feces of captive Japanese macaques (M. fuscata) in an open-air corral in Japan. The sequence of the 18S rRNA gene in the isolates differed from the P19-061405 strain in 2 nucleotide positions, but was identical to the EHMfas1 strain isolated previously from a cynomolgus monkey (M. fascicularis). One of the E. nuttalli isolates from Japanese macaques, named the NASA6 strain, was axenized and cloned. In isoenzyme analysis, the mobilities of hexokinase and phosphate glucose isomerase in the NASA6 strain were identical to those in the P19-061405 and EHMfas1 strains, but the mobility of phosphoglucomutase was different. These results were supported by gene analyses of these enzymes. Inoculation of NASA6 strain trophozoites into the liver of hamsters led to formation of an amoebic liver abscess. The liver lesions were characterized by extensive necrosis associated with inflammatory reactions. These results demonstrate that the NASA6 strain is potentially virulent and that E. nuttalli should be recognized as a common parasite in macaques.
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PMID:Isolation and characterization of a potentially virulent species Entamoeba nuttalli from captive Japanese macaques. 1963 74