ALKYL DIHYDROXYACETONE PHOSPHATE SYNTHASE IN GLYCOSOMES OF TRYPANOSOMA-BRUCEI

Alkyl-dihydroxyacetone phosphate synthase (E.C. 2.5.1.26), the key enz yme in ether phospholipid biosynthesis, was demonstrated to be present in Trypanosoma brucei, The distribution of alkyl-dihydroxyacetone pho sphate synthase was found to be identical to that of dihydroxyacetone phosphate acyltransferase (E.C. 2.3.1.42), which has previously been s hown to be exclusively associated with the glycosome fraction (Opperdo es, F.R. (1984) FEES Lett. 169, 35-39). Studies with gradient purified glycosomes indicated that the formation of alkyl-dihydroxyacetone pho sphate was completely dependent on the presence of acyl-dihydroxyaceto ne phosphate. The glycosomal alkyl-dihydroxyacetone phosphate synthase activity was characterized with respect to its pH optimum, Triton X-1 00 sensitivity and the dependency on the concentration of the substrat es palmitoyl-dihydroxyacetone phosphate and hexadecanol. Using thin-la yer chromatographic and alkaline hydrolysis procedures the reaction pr oduct was identified as alkyl-dihydroxyacetone phosphate. Alkyl-dihydr oxyacetone phosphate synthase was resistant to proteolytic inactivatio n by trypsin in intact glycosomes but not in Triton X-100 disrupted gl ycosomes. It is concluded that T. brucei glycosomes contain the enzyme s responsible for glycero-ether bond formation analogous to mammalian peroxisomes.