Evolutionary relationships of the glucokinase from the amitochondriate protist, Trichomonas vaginalis

Two genes coding for Trichomonas vaginalis glucokinase were isolated and sequenced. The putative translation products have molecular masses of 41584 and 41772 Da, corresponding to 375 and 377 amino acids, respectively. These values agree with data determined by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for the enzyme purified from the organism. The two sequences showed 78% amino acid identity. The sequences and their phylogenetic reconstruction show that they are members of a glucokinase/fructokinase protein family found in eubacteria and also in the eukaryote Giardia lamblia and are only distantly related to typical eukaryotic hexokinases. The results indicate that the evolutionary past of this enzyme, catalyzing the first step of glycolysis in T. vaginalis, is different from that of the enzyme performing this key role in almost all other eukaryotes. (C) 2001 Elsevier Science B.V. All rights reserved.