Sphingolipids are essential components of eukaryotic cell membranes, 
particularly the plasma membrane, and are involved in a diverse array of signal 
transduction pathways. Mammals produce sphingomyelin (SM) as the primary complex 
sphingolipid via the well characterised SM synthase. In contrast yeast, plants 
and some protozoa utilise an evolutionarily related inositol phosphorylceramide 
(IPC) synthase to synthesise IPC. This activity has no mammalian equivalent and 
IPC synthase has been proposed as a target for anti-fungals and anti-protozoals. 
However, detailed knowledge of the sphingolipid biosynthetic pathway of the 
apicomplexan protozoan parasites was lacking. In this study bioinformatic 
analyses indicated a single copy orthologue of the putative SM synthase from the 
apicomplexan Plasmodium falciparum (the causative agent of malaria) was a bona 
fide sphingolipid synthase in the related model parasite, Toxoplasma gondii 
(TgSLS). Subsequently, TgSLS was indicated, by complementation of a mutant cell 
line, to be a functional orthologue of the yeast IPC synthase (AUR1p), 
demonstrating resistance to the well characterised AUR1p inhibitor aureobasidin 
A. In vitro, recombinant TgSLS exhibited IPC synthase activity and, for the 
first time, the presence of IPC was demonstrated in T. gondii lipid extracts by 
mass spectrometry. Furthermore, host sphingolipid biosynthesis was indicated to 
influence, but be non-essential for, T. gondii proliferation, suggesting that 
whilst scavenging does take place de novo sphingolipid synthesis may be 
important for parasitism.