The phospholipid cardiolipin, or diphosphatidylglycerol, is ubiquitous in 
eucaryotes. It is unique in structure, subcellular localization, and potential 
function. Because it is found predominantly in the mitochondrial inner membrane, 
it is an excellent marker for mitochondrial biogenesis. Cardiolipin is required 
for activity of several mitochondrial enzymes and possibly also for import of 
proteins into the mitochondrion. To understand the role of cardiolipin in these 
cellular events, it is necessary to characterize the enzymes of the cardiolipin 
pathway, as well as the genes that control the expression of these enzymes. To 
date, the structural genes encoding the cardiolipin biosynthetic enzymes have 
not been identified in any eucaryotic organism. However, considerable 
information is available regarding the regulation of this pathway in yeast. The 
activity and regulation of the first enzyme of the pathway, 
CDP-diacylglycerol:sn-glycerol-3-phosphate 3-phosphatidyltransferase 
(phosphatidylglycerophosphate (PGP) synthase, EC 2.7.8.5), has been 
characterized in two evolutionarily divergent yeasts, Saccharomyces cerevisiae 
and Schizosaccharomyces pombe. In contrast to the second and third enzymes of 
the pathway, this enzyme is highly regulated, both by cross-pathway control and 
by factors affecting mitochondrial development. PGP synthase from S. pombe (and 
cardiolipin synthase from S. cerevisiae) have been purified to homogeneity. The 
amino acid sequences of these enzymes, combined with the availability of the 
complete genome sequence from S. cerevisiae will simplify the cloning of these 
genes in the near future.