E. Saavedralira et al., EXPRESSION AND CHARACTERIZATION OF RECOMBINANT PYRUVATE PHOSPHATE DIKINASE FROM ENTAMOEBA-HISTOLYTICA, Biochimica et biophysica acta. Protein structure and molecular enzymology, 1382(1), 1998, pp. 47-54
The parasite Entamoeba histolytica is an organism whose main energetic
source comes from glycolysis. It has the singularity that several of
its glycolytic enzymes use pyrophosphate as an alternative phosphate d
onor. Thus, pyruvate phosphate dikinase (PPDK), an inorganic pyrophosp
hate (PPi)-dependent enzyme, substitutes pyruvate kinase present in hu
mans. We previously cloned and sequenced the gene that codifies for PP
DK in E. hisyolytica. We now report its expression in a bacterial syst
em and its purification to 98% homogeneity. We determined its K-m for
phosphoenolpyruvate, AMP and PPi (21, < 5 and 100 mu M, respectively).
Unlike PPDK from maize and bacteria and pyruvate kinase from other ce
lls, EhPPDk is dependent on divalent cations but does not require mono
valent cations for activity. The enzyme has an optimum pH of 6.0, it i
s labile to low temperatures and has a tetrameric structure. Since EhP
PDK is a PPi-dependent enzyme, we also tested the effect of some pyrop
hosphate analogs as inhibitors of activity. Studies on the function an
d structure of this enzyme may be important for therapeutic research i
n several parasitic diseases, since it has no counterpart in humans. (
C) 1998 Elsevier Science B.V.