Characterization of the glyoxalases of the malarial parasite Plasmodium falciparum and comparison with their human counterparts.
The glyoxalase system consisting of glyoxalase I (GloI) and glyoxalase II (GloII) constitutes a glutathione-dependent intracellular pathway converting toxic 2-oxoaldehydes, such as methylglyoxal, to the corresponding 2-hydroxyacids. Here we describe a complete glyoxalase system in the malarial parasite Plasmodium falciparum. The biochemical, kinetic and structural properties of cytosolic GloI (cGloI) and two GloIIs (cytosolic GloII named cGloII, and tGloII preceded by a targeting sequence) were directly compared with the respective isofunctional host enzymes. cGloI and cGloII exhibit lower K(m) values and higher catalytic efficiencies (k(cat)/K(m) ) than the human counterparts, pointing to the importance of the system in malarial parasites. A Tyr185Phe mutant of cGloII shows a 2.5-fold increase in K(m) , proving the contribution of Tyr185 to substrate binding. Molecular models suggest very similar active sites/metal binding sites of parasite and host cell enzymes. However, a fourth protein, which has highest similarities to GloI, was found to be unique for malarial parasites; it is likely to act in the apicoplast, and has as yet undefined substrate specificity. Various S-(N-hydroxy-N-arylcarbamoyl)glutathiones tested as P. falciparum Glo inhibitors were active in the lower nanomolar range. The Glo system of Plasmodium will be further evaluated as a target for the development of antimalarial drugs.
Akoachere
Monique
M
Interdisciplinary Research Center, Heinrich-Buff-Ring 26-32, Justus-Liebig University, D-35392 Giessen, Germany.
Iozef
Rimma
R
Rahlfs
Stefan
S
Deponte
Marcel
M
Mannervik
Bengt
B
Creighton
Donald J
DJ
Schirmer
Heiner
H
Becker
Katja
K
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D005786:Gene Expression Regulation; D005978:Glutathione / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D007791:Lactoylglutathione Lyase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics; D008670:Metals / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000201:enzymology*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment; D013869:Thiolester Hydrolases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics; D000099301:Hydroxyacylglutathione Hydrolase
D005978:Glutathione; D007791:Lactoylglutathione Lyase; D008670:Metals; D011994:Recombinant Proteins; D013869:Thiolester Hydrolases; D000099301:Hydroxyacylglutathione Hydrolase