cd09135

Catalytic domain, repeat 1, of eukaryotic PhosphatidylGlycerophosphate Synthases; Catalytic domain, repeat 1, of eukaryotic phosphatidylglycerophosphate (PGP) synthases, also called CDP-diacylglycerol--glycerol-3-phosphate 3-phosphatidyltransferase (EC 2.7.8.5). Eukaryotic PGP synthases are different and unrelated to prokaryotic PGP synthases and yeast phosphatidylserine synthase. They catalyze the synthesis of PGP from CDP-diacylglycerol and sn-glycerol 3-phosphate, the committed and rate-limiting step in the biosynthesis of cardiolipin (CL), which is an essential component of many mitochondrial functions in eukaryotes. Members in this subfamily all have two HKD motifs (H-x-K-x(4)-D, where x represents any amino acid residue) that characterizes the phospholipase D (PLD) superfamily. They may utilize a common two-step ping-pong catalytic mechanism involving a substrate-enzyme intermediate to cleave phosphodiester bonds. The two motifs are suggested to constitute the active site involved in the phosphatidyl group transfer.