Abstract
1. 1. The activity of the following enzymes involved in the biosynthesis of porphyrins was determined in endosymbiote-free and endosymbiote-containing Crithidia deanei grown in a chemically defined medium: succinyl Coenzyme A synthetase (Suc.CoA-S), 5-aminolevulinate synthetase (ALA-S), 4,5-dioxovaleric acid transaminase (DOVA-T), 5-aminolevulinate dehydratase (ALA-D), por- phobilinogenase (PBGase), deaminase and heme synthetase (Heme-S). The amount of 5-aminolevulinic acid (ALA) and porphobilinogen, porphyrins and heme was also determined. 2. 2. ALA and PBG were detected in C. deanei. The levels of free porphyrins was low. Heme concentration was nil. 3. 3. The activity of ALA-D. deaminase and PBGase was not detected in C deanei. 4. 4. The activity of Suc.CoA-S and ALA-S were twice higher in symbiote-containing than in aposymbiotic C. deanei. Aposymbiotic cells had a higher activity of DOVA-T than symbiote-containing cells. 5. 5. The level of Heme-S, measured using protoporphyrin as substrate, was twice as high in symbiotecontaining than in symbiote-free cells,
Highlights
Crithidia deanei, a flagellated trypanosomatid protozoan, isolated from the hemipteran Zelus leucogramus and harboring endosymbiote (Mundim er al., 1974) was made aposymbiotic with high doses of chloramphenicol (Mundim and Roitman, 1977)
Taking into account the currently accepted porphyrin pathway (Fig. I), we have investigated several enzymic activities in the heme biosynthetic chain in symbiote-bearing and symbiote-free strains of C. deunei
C. oncolpeti and Blustocrithidiu cu1ki.r (Chang and Sassa. 1975) harboring endosymbiotic bacterium-like organisms in a hemin-free medium suggests that the endosymbiotcs contribute to the host flagellate with heme biosynthetic capability
Summary
A flagellated trypanosomatid protozoan, isolated from the hemipteran Zelus leucogramus and harboring endosymbiote (Mundim er al., 1974) was made aposymbiotic with high doses of chloramphenicol (Mundim and Roitman, 1977). A chemically defined medium supports growth of both normal and aposymbiotic strains (Roitman et ul., 1972). Such intracellular symbiotes are integrated into the physiology of the host cell (McGhee and Cosgrove, 1980). Nutritional studies carried out in flagellate trypanosomatids have clearly demonstrated that heme compounds, including hemin, hematin or hemoglobin, are essential growth factors (Lwoff, 1951). Such nutritional requirements are associated with their inability for heme biosynthesis (Roitman et al, 1972; Chang and Sassa, 1975).
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