Protozoa purine metabolism

Purine and pyrimidine nucleotides are essential components of many biochemical molecules, from DNA and RNA to ATP and NAD. In recent years, the pyrimidine and especially the purine metabolism of parasitic helminths have been investigated extensively, mainly because they are different from the pathways in the mammalian host such that they have potential as targets for chemotherapeutic attack. For a review of purine and pyrimidine pathways in parasitic helminths and protozoa, see Berens et al. (1995). Although parasitic helminths do not synthesize purines de novo, but obtain them from the host, they do possess elaborate purine salvage pathways for a more economical management of this resource. Pyrimidines, on the other hand, are synthesized de novo by all parasitic flat-worms studied so far and, as with mammalian... 

Marr, J. J. (1991) Purine metabolism in parasitic protozoa and its relationship to chemotherapy. In Biochemical Protozoology (eds Coombs, G. and North, M.) Taylor and Francis, London pp. 524-536. 

For further information on purine metabolism in protozoa, see Hitchings... 

It is of historical interest that Tetrahymena gelii, whose metabolism has been described in detail [387], is inhibited by 8-azaguanine [388] and other purine analogues [389, 390]. Of more importance to chemotherapy is the fact that pathogenic protozoa such as the trypanosomes respond in vitro to a number of... 

The mechanism of inhibition of these protozoal infections by the most active drugs, puromycin and the aminonucleoside, is not known. Puromycin and nucleocidin both interfere with protein synthesis, but the aminonucleoside does not. It is known to be demethylated to 3 -amino-3-deoxyadenosine, which is phosphorylated and interferes with nucleic acid metabolism (see above). Whether puromycin must be converted to the aminonucleoside before it can inhibit protozoa has not been established. Some purine analogues known to interfere with nucleic acid metabolism, however, are less effective as antiprotozoal agents, even in vitro, perhaps because their effects are primarily on the de novo pathway which many, if not all, protozoa do not use [406]. 

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