A trypanothione-dependent glyoxalase I with a prokaryotic ancestry in Leishmania major

Abstract

Glyoxalase I forms part of the glyoxalase pathway that detoxifies reactive aldehydes such as methylglyoxal, using the spontaneously formed glutathione hemithioacetal as substrate. All known eukaryotic enzymes contain zinc as their metal cofactor, whereas the Escherichia coli glyoxalase I contains nickel. Database mining and sequence analysis identified putative glyoxalase I genes in the eukaryotic human parasites Leishmania major, Leishmania infantum, and Trypanosoma cruzi, with highest similarity to the cyanobacterial enzymes. Characterization of recombinant L. major glyoxalase I showed it to be unique among the eukaryotic enzymes in sharing the dependence of the E. coli enzyme on nickel. The parasite enzyme showed little activity with glutathione hemithioacetal substrates but was 200-fold more active with hemithioacetals formed from the unique trypanosomatid thiol trypanothione. L. major glyoxalase I also was insensitive to glutathione derivatives that are potent inhibitors of all other characterized glyoxalase I enzymes. This substrate specificity is distinct from that of the human enzyme and is reflected in the modification in the L. major sequence of a region of the human protein that interacts with the glycyl-carboxyl moiety of glutathione, a group that is conjugated to spermidine in trypanothione. This trypanothione-dependent glyoxalase I is therefore an attractive focus for additional biochemical and genetic investigation as a possible target for rational drug design.methylglyoxal ͉ D-lactate ͉ glutathione ͉ nickel

Glyoxalase biochemistry

“…Numerous Glo1 enzymes are widespread in nature, yet a few organisms appear not to harbor a Glo1 enzyme. Although T. brucei appears to lack Glo1 (although T. brucei is suggested to have a MG reductase that reduces MG to L-lactataldehyde as mentioned previously), T. cruzi does contain an active Glo1 (44,48,49). Giardia lamblia and Entamoeba histolytica however, lack Glo1 based on genome analyses (49).…”

“…For example, the Leishmania major Glo1 was reported to lack Zn 2+ -activation, but was found to be fully active in the presence of Ni 2+ ion (48). Additionally this enzyme was found to utilize the cellular thiol trypanothione (bis(glutathionyl)spermidine) as the thiol co-substrate for the enzyme ( Figure 5).…”

Niche metabolism in parasitic protozoa

“…Just as was the case with the study of the evolution of the Apicomplexa, the continued characterization of such possible traits (Wilkinson et al 2002;Allen et al 2004;Vickers et al 2004) continues to point towards a possibility that the unusual organellar metabolism of extant trypanosomatids has been shaped through contact and lateral gene transfer with a photosynthetic or secondarily nonphotosynthetic microbe.…”

Potential role of the glyoxalase pathway as a drug target in Leishmania infantum: an exact steady-state model analysis

“…Trypanosomatids, such as Leishmania infantum, are pathogenic microbial parasites which have glycolytic enzymes located in a specific cell organelle, the glycosome [3]. In these organisms, the usual glyoxalase cofactor glutathione is functionally replaced by trypanothione [4,5]. Inhibition of the glyoxalase pathway might cause the accumulation of methylglyoxal in the glycosome, hampering glycolysis and killing the parasite.…”