Alkyl dihydroxyacetone phosphate synthase in glycosomes of Trypanosoma brucei

Abstract

Alkyl-dihydroxyacetone phosphate synthase (E.C. 2.5.1.26), the key enzyme in ether phospholipid biosynthesis, was demonstrated to be present in Trypanosoma brucei. The distribution of alkyl-dihydroxyacetone phosphate synthase was found to be identical to that of dihydroxyacetone phosphate acyltransferase (E.C. 2.3.1.42), which has previously been shown to be exclusively associated with the glycosome fraction (Opperdoes, F.R. (1984) FEBS Lett. 169, 35–39). Studies with gradient purified glycosomes indicated that the formation of alkyl-dihydroxyacetone phosphate was completely dependent on the presence of acyl-dihydroxyacetone phosphate. The glycosomal alkyl-dihydroxyacetone phosphate synthase activity was characterized with respect to its pH optimum, Triton X-100 sensitivity and the dependency on the concentration of the substrates palmitoyl-dihydroxyacetone phosphate and hexadecanol. Using thin-layer chromatographic and alkaline hydrolysis procedures the reaction product was identified as alkyl-dihydroxyacetone phosphate. Alkyl-dihydroxyacetone phosphate synthase was resistant to proteolytic inactivation by trypsin in intact glycosomes but not in Triton X-100 disrupted glycosomes. It is concluded that T. brucei glycosomes contain the enzymes responsible for glycero-ether bond formation analogous to mammalian peroxisomes.