5-Aminolevulinic acid synthesis in epimastigotes of Trypanosoma cruzi.
OBJECTIVE
Trypanosoma cruzi is the causative agent of Chagas disease or American trypanosomiasis. The parasite manifests a nutritional requirement for heme compounds because of its biosynthesis deficiency. The aim of this study has been to investigate the presence of metabolites and enzymes of porphyrin pathway, as well as ALA formation in epimastigotes of T. cruzi, Tulahuén strain, Tul 2 stock.


METHODS
Succinyl CoA synthetase, 5-aminolevulinic acid (ALA) synthetase, 4,5-dioxovaleric (DOVA) transaminase, ALA dehydratase and porphobilinogenase activities, as well as ALA, porphobilinogen (PBG), free porphyrins and heme content were measured in a parasite cells-free extract. Extracellular content of these metabolites was also determined.


RESULTS
DOVA, PBG, porphyrins and heme were not detected in acellular extracts of T. cruzi. However ALA was detected both intra- and extracellularly This is the first time that the presence of ALA (98% of intracellularly formed ALA) is demonstrated in the extracellular medium of a parasite culture. Regarding the ALA synthesizing enzymes, DOVA transaminase levels found were low (7.13+/-0.49EU/mg protein), whilst ALA synthetase (ALA-S) activity was undetectable. A compound of non-protein nature, low molecular weight, heat unstable, inhibiting bacterial ALA-S activity was detected in an acellular extract of T. cruzi. This inhibitor could not be identified with either ALA, DOVA or heme.


CONCLUSIONS
ALA synthesis is functional in the parasite and it would be regulated by the heme levels, both directly and through the inhibitor factor detected. ALA formed can not be metabolized further, because the necessary enzymes are not active, therefore it should be excreted to avoid intracellular cytotoxicity.
Lombardo
María Elisa
ME
Centro de Investigaciones sobre Porfirinas y Porfirias-CIPYP (CONICET-FCEN, UBA), Ciudad Universitaria Pabellón II 2do, Piso, 1428 Buenos Aires, Argentina.
Araujo
Lidia Susana
LS
Batlle
Alcira
A
D000624:5-Aminolevulinate Synthetase / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D000622:Aminolevulinic Acid / Q000378:metabolism*; D000642:Ammonia-Lyases / Q000378:metabolism; D000818:Animals; D006418:Heme / Q000378:metabolism; D011162:Porphobilinogen / Q000378:metabolism; D012242:Rhodobacter sphaeroides / Q000201:enzymology; D013389:Succinate-CoA Ligases / Q000378:metabolism; D000637:Transaminases / Q000378:metabolism; D014349:Trypanosoma cruzi / Q000201:enzymology*
D006418:Heme; D011162:Porphobilinogen; D000622:Aminolevulinic Acid; D000624:5-Aminolevulinate Synthetase; D000637:Transaminases; C019687:aminolevulinate aminotransferase; D000642:Ammonia-Lyases; C100132:porphobilinogenase; D013389:Succinate-CoA Ligases