Abstract
The enzymes glyoxalase 1 and 2 (Glo1 and Glo2) are found in most eukaryotes and catalyze the glutathione-dependent conversion of 2-oxoaldehydes to 2-hydroxycarboxylic acids. Four glyoxalases are encoded in the genome of the malaria parasite Plasmodium falciparum, the cytosolic enzymes PfGlo1 and PfcGlo2, the apicoplast enzyme PftGlo2, and an inactive Glo1-like protein that also carries an apicoplast-targeting sequence. Inhibition or knockout of the Plasmodium glyoxalases was hypothesized to lead to an accumulation of 2-oxoaldehydes and advanced glycation end-products (AGE) in the host-parasite unit and to result in parasite death. Here, we generated clonal P. falciparum strain 3D7 knockout lines for PFGLO1 and PFcGLO2 using the CRISPR-Cas9 system. Although 3D7Δglo1 knockout clones had an increased susceptibility to external glyoxal, all 3D7Δglo1 and 3D7Δcglo2 knockout lines were viable and showed no significant growth phenotype under standard growth conditions. Furthermore, the lack of PfcGlo2, but not PfGlo1, increased gametocyte commitment in the knockout lines. In summary, PfGlo1 and PfcGlo2 are dispensable during asexual blood-stage development while the loss of PfcGlo2 may induce the formation of transmissible gametocytes. These combined data show that PfGlo1 and PfcGlo2 are most likely not suited as targets for selective drug development.
Highlights
In 1990, Vander Jagt et al reported that Plasmodium falciparum-infected erythrocytes do consume much more glucose than uninfected erythrocytes, and produce up to 30-times more D-lactate owing to a highly efficient glyoxalase system [1]
We found that PfGlo1 and PfcGlo2 are both dispensable for asexual blood-stage development while the loss of PfcGlo2 results in increased gametocyte commitment rates
Gene multiplications or other genetic events that might have resulted in functional PfGlo1 or PfcGlo2 were excluded by western blot analysis with specific antibodies (Fig. 1D), revealing that all clonal knockout strains lacked either PfGlo1 or PfcGlo2 as expected (Fig. 1E)
Summary
In 1990, Vander Jagt et al reported that Plasmodium falciparum-infected erythrocytes do consume much more glucose than uninfected erythrocytes, and produce up to 30-times more D-lactate owing to a highly efficient glyoxalase system [1]. Since this seminal study, the P. falciparum glyoxalases have gained considerable attention as model enzymes [2,3,4,5] and as potential targets for rational drug development [6,7,8,9,10].
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