Tafazzin is a putative enzyme that is involved in cardiolipin metabolism, it may 
carry mutations responsible for Barth syndrome. To identify the biochemical 
reaction catalyzed by tafazzin, we expressed the full-length isoform of 
Drosophila melanogaster tafazzin in a baculovirus-Sf9 insect cell system. 
Tafazzin expression induced a new enzymatic function in Sf9 cell mitochondria, 
namely 1-palmitoyl-2-[14C]linoleoyl-phosphatidylcholine:monolysocardiolipin 
linoleoyltransferase. We also found evidence for the reverse reaction, because 
tafazzin expression caused transfer of acyl groups from phospholipids to 
1-[14C]palmitoyl-2-lyso-phosphatidylcholine. An affinity-purified tafazzin 
construct, tagged with the maltose-binding protein, catalyzed both forward and 
reverse transacylations between cardiolipin and phosphatidylcholine, but was 
unable to utilize CoA or acyl-CoA as substrates. Whereas tafazzin supported 
transacylations between various phospholipid-lysophospholipid pairs, it showed 
the highest rate for the phosphatidylcholine-cardiolipin transacylation. 
Transacylation activities were about 10-fold higher for linoleoyl groups than 
for oleoyl groups, and they were negligible for arachidonoyl groups. The data 
show that Drosophila tafazzin is a CoA-independent, acyl-specific phospholipid 
transacylase with substrate preference for cardiolipin and phosphatidylcholine.