Lack of Arginine Decarboxylase in Trypanosoma cruzi Epimastigotes

Abstract

The presence of arginine decarboxylase (ADC) enzymatic activity in Trypanosoma cruzi epimastigotes is still a matter of controversy due to conflicting results published during the last few years. We have investigated whether arginine might indeed be a precursor of putrescine via agmatine in these parasites. We have shown that wild-type T. cruzi epimastigotes cultivated in a medium almost free of polyamines stopped their growth after several repeated passages of cultures in the same medium, and that neither arginine nor omithine were able to support or reinitiate parasite multiplication. In contrast, normal growth was quickly resumed after adding exogenous putrescine or spermidine. The in vivo labelling of parasites with radioactive arginine showed no conversion of this amino acid into agmatine, and attempts to detect ADC activity measured by the release of CO2 under different conditions in T. cruzi extracts gave negligible values for all strains assayed. The described data clearly indicate that wild-type T. cruzi epimastigotes lack ADC enzymatic activity.

Polyamine biosynthetic enzymes as drug targets in parasitic protozoa

“…In fact, putrescine uptake is 10-50-fold higher in T. cruzi than in Leishmania mexicana and C. fasciculata [6]. Lack of ODC and the inability to synthesize putrescine is consistent with the following findings : (i) that T. cruzi is dependent on uptake of diamines [15], (ii) that DFMO is completely inactive against all stages of the parasite, (iii) that expression of a foreign ODC gene in T. cruzi overcomes the requirement of exogenous polyamines for growth [15] and (iv) that DFMO treatment causes growth arrest of T. cruzi that express a foreign ODC [16].…”

Contributions of Ultrastructural Studies to the Cell Biology of Trypanosmatids: Targets for Anti-Parasitic Drugs

“…Interference in the synthesis of polyamines with eflornithine or DFMO (difluoromethylornithine), a selective irreversible inhibitor of ornithine decarboxylase (ODC), induces changes in the differentiation process in T. b. gambiense. However, it was not effective against Leishmania or T. cruzi due to differences in the gene and an inability to produce significant amounts of putrescine, respectively [60][61][62][63]. Use of the putrescine analogue 1,4-diamino-2-butanone (DAB) caused inhibition of the proliferation of Leishmania and T. cruzi and severe damage to the mitochondrion characterized by swelling, fenestration and the presence of few cristae [64][65][66][67][68].…”

Ornithine decarboxylase and S-adenosylmethionine decarboxylase in trypanosomatids

“…All attempts to measure any ODC activity in this parasite have been unsuccessful and it was suggested that the parasite contains an alternative pathway for the production of putrescine from arginine, via agmatine [30]. However, gene analysis as well as metabolic studies using radiolabelled ornithine and arginine together with the relevant enzyme assays indicate that T. cruzi is unable to synthesize significant amounts of putrescine, and is dependent on scavenging this diamine from an external source (like the host) [31][32][33]. The parasite has been shown to contain highly effective high-affinity transporters for the uptake of putrescine [34] and spermidine [35].…”

“…T. brucei, on the other hand, replicates extracellularly in the bloodstream of the host and is thus more dependent on endogenous polyamines (the polyamine concentration in blood is relatively low). The introduction of the Odc gene from C. fasciculata into the genome of T. cruzi makes the parasite overcome the exogenous putrescine requirement for growth [36]. Interestingly, the C. fasciculata is a stable enzyme when expressed in T. cruzi [36].…”

“…The introduction of the Odc gene from C. fasciculata into the genome of T. cruzi makes the parasite overcome the exogenous putrescine requirement for growth [36]. Interestingly, the C. fasciculata is a stable enzyme when expressed in T. cruzi [36]. The recent identification and characterization of a polyamine transporter from L. major may facilitate the identification of the specific putrescine transporter responsible for the uptake of putrescine in T. cruzi [37].…”