Trypanosome sterols and their metabolic origins

1. 1. Chromatographic and chemical analyses show that up to four major sterols may be present in blood and culture forms of trypanosomes. 2. 2. Blood and culture forms of Trypanosoma lewisi and culture forms of T. rhodesiense biosynthesize C(24)-alkyl sterols de novo. In these trypanosomes, and in blood forms of T. rhodesiense, exogenous cholesterol is incorporated and esterified, but not further metabolized. 3. 3. Changes in sterol composition and metabolism occur in T. lewisi during “maturation” in vivo, and during in vitro culture. 4. 4. The role of sterol biosynthesis in cyclical mitochondrial biogenesis in trypanosomes is discussed, and also the evolutionary significance of the phytosterols identified in this study.