Purine metabolism in Trichomonas vaginalis.

The purine metabolism of several genera of parasitic protozoa, is of interest partly due to their sensitivity to purine analogues, and to differences in the enzymes of purine metabolism compared to mammalian systems [l-6]. Trichomonas vaginalis, the causative agent of trichomonal vaginitis, a mild, but very common, sexually-transmitted disease, has not been studied in this respect; there is a general lack of knowledge on the biosynthetic ability of the organism. We report here on the ability of washed-cell suspensions of T. vaginalis to salvage the purine bases, adenine and guanine, and their nucleosides, and on the absence from the organism of the ability to synthesise purines de novo and to interconvert purine nucleotides. Examination of possible purine salvage enzymes suggests that nucleoside phosphorylase and nucleoside kinase activities are responsible for the conversion of purine bases and nucleosides to nucleoside monophosphates; purine phosphoribosyltransferases are either absent or present at only very low levels.