DETECTION OF UBIQUINONE IN PARASITIC AND FREE-LIVING PROTOZOA, INCLUDING SPECIES DEVOID OF MITOCHONDRIA

Ubiquinone (coenzyme Q, CoQ) was analyzed and individual homologues qu antified in 11 species of parasitic and free-living protozoa by a comb ination of thin-layer chromatography and high performance liquid chrom atography. Fast atom bombardment ionization-mass spectrometry was used for the first time to confirm the identity of the fractionated CoQ ho mologues and proved to be a fast, gentle and convenient method for ubi quinone identification. Ubiquinone was detected in all organisms inclu ding those devoid of identifiable mitochondria. However, significantly lower levels of CoQ were present in those organisms lacking this resp iratory organelle (5- to 50-fold lower in Entamoeba histolytica (CoQ(9 )) and 15- to 350-fold for Giardia lamblia (CoQ(9)) and Tritrichomonas foetus (CoQ(10))). Coenzyme Q(9) was the predominant homologue in pro mastigotes of Leishmania donovani and Leishmania major. Lower amounts of CoQ(8) and CoQ(10) were also detected in L. donovani, and CoQ(8) in L. major. Comparison of the in vitro cultivated promastigote and amas tigote forms of Leishmania pifanoi and Leishmania amazonensis revealed CoQ(9) to be the sole detectable ubiquinone homologue in the amastigo te (macrophage) stage, whereas CoQ(8) and CoQ(10) were also present in the promastigotes (life cycle stage found in the insect gut) of L. pi fanoi, and CoQ(7) and CoQ(8) in promastigotes of L. amazonensis. Inter estingly, the total amounts of CoQ were similar in both forms of these organisms. The free-living ciliates, Tetrahymena thermophila and Para mecium tetraurelia contained CoQ(8) as the predominant ubiquinone spec ies and this homologue was also present in the isolated cilia from P. tetraurelia. The marine ciliate, Parauronema acutum contained CoQ(7) a s well as CoQ(8). Comparison of xenosome-containing P. acutum with org anisms lacking the symbiont revealed that twice the level of CoQ(8) wa s present in cells grown with this cytoplasmic gram-negative bacterium . Results suggest that CoQ is ubiquitous amongst the protozoa, regardl ess of the presence of mitochondria, and may function in alternative r oles to that of mitochondrial electron transport chain component.