Molecular biology of the hexokinase isoenzyme pattern that distinguishes pathogenic Entamoeba histolytica from nonpathogenic Entamoeba dispar

The electrophoretic patterns of hexokinase and phosphoglucomutase have been widely used to distinguish Entamoeba histolytica from Entamoeba dispar isolates. Although E. histolytica and E. dispar, previously called pathogenic and nonpathogenic Entamoeba histolytica, differ clearly in sequences of many homologous genes, a conversion between the two has been reported by several laboratories, in each case showing the conversion of hexokinase (ATP, d-hexose 6-phosphotransferase, EC 2.7.1.1) isoenzyme patterns. An apparent mobility shift of this enzyme may either be due to posttranslational modification or processing, or to the appearance of a new isoform encoded by a second gene. In this study we observed that the four observed bands in the isoenzyme patterns of pathogenic and nonpathogenic forms of Entamoeba were correlated with four different cDNAs, and that the four recombinant hexokinases produced in Escherichia coli comigrated with their natural counterparts. Polymerase chain reaction (PCR) experiments did not reveal hidden genes which might be responsible for conversion phenomena. These results strongly support the redefinition of pathogenic and nonpathogenic Entamoeba histolytica as two closely related species Entamoeba histolytica and Entamoeba dispar.