Trypanosomatidae: Isoleucine Requirement and Threonine Deaminase in Species With and Without Endosymbionts

Among the trypanosomatid protozoa, biosynthetic threonine deaminase was found exclusively in species harboring symobionts: Crithidia oncopelti, C. deanei , and Blastocrithidia culicis but not in other species examined nor in symbiont-free strains of symbiont-harboring species. By cell fractionation...

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Veröffentlicht in:Experimental parasitology 1982-01, Vol.5 (3), p.371-380
Hauptverfasser: Alfieri, S C, Camargo, E P
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Sprache:eng
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Zusammenfassung:Among the trypanosomatid protozoa, biosynthetic threonine deaminase was found exclusively in species harboring symobionts: Crithidia oncopelti, C. deanei , and Blastocrithidia culicis but not in other species examined nor in symbiont-free strains of symbiont-harboring species. By cell fractionation of C. deanei , a symbiont-rich subcellular fraction was isolated in which the specific activity of threonine deaminase was 10 times higher than that of crude homogenates. These results indicate that, in trypanosomatids, only species harboring a symbiont are capable of isoleucine synthesis and that threonine deaminase, the first enzyme of the isoleucine biosynthetic pathway, actually belongs to the symbiont. Species with symbionts do not require for growth either isoleucine or the metabolically related valine and leucine.
ISSN:0014-4894