Phosphatidate cytidylyltransferase

PHOSPHATIDATE PHOSPHATASE PHOSPHATIDATE CYTIDYLYLTRANSFERASE PHOSPHATIDATE PHOSPHATASE Phosphatidolipase,... 

Fig. 6. Synthesis of phospholipid polar head groups. The three major phospholipid species in E. coli are synthesized by a total of six different enzymatic activities (1) phosphatidate cytidylyltransferase (Cds), (2) phosphatidylserine synthase (PssA), (3) phosphatidylserine decarboxylase (Psd), (4) phosphatidyl-glycerol phosphate synthase (PgsA), (5) phosphatidylglycerol phosphate phosphatase (PgpA or PgpB), and (6) cardiolipin synthase (els).

CTP phosphatidate cytidylyltransferase has been observed in plastids, mitochondria, and ER. In all three compartments, the CDP-diacylglycerol derived from phosphatidic acid is used in the synthesis of phosphatidylglycerol in mitochondria, the reaction of phosphatidylglycerol with a second CDP-diacylglycerol then produces cardiolipin. The ER can also incorporate CDP-diacylglycerol into phosphatidylinositol and phosphatidylserine. 

This enzyme [EC 2.7.7.41], also known as CTP phospha-tidate cytidylyltransferase and CDP-diacylglycerol synthase, catalyzes the reaction of CTP with phosphatidate to produce CDP-diacylglycerol and pyrophosphate. 

Lyso-PtdCho is not simply a lipid metabolite producing neurotrophic and neurotoxic effects. It participates in many signal transduction processes. Lyso-PtdCho activates protein kinases such as protein kinase C, protein kinase A, and c-jun terminal kinase. Lyso-PtdCho stimulates phospholipase D and inhibits CTP-phosphocholine cytidylyltransferase (Gomez-Munoz et al., 1999 Boggs et al., 1995). Lyso-PtdCho acts as an agonist for certain G-protein coupled receptors and can be converted to another bioactive lipid, lyso-phosphatidic acid. 

CTP phosphocholine cytidylyltransferase (3) glycerol kinase (4) acyl-CoA glycerol-3-phosphate acyltransferase (5) acyl-CoA acyl glycerol-3-phosphate acyltransferase (6) phosphatidic acid phosphatase (7) CDP-choline diacylglycerol phosphocholine transferase. 

Fig. 1. Phospholipid biosynthetic pathways in animal cells. The abbreviations are DHAP, dihydroxyacetone phosphate G-3-P, glycerol-3-phosphate PA, phosphatidic acid DG, diacylglycerol CDP-DG, cytidine diphosphodiacylglycerol PI, phosphatidylinositol PG, phosphatidylglycerol PG-P, phosphatidylglycerol phosphate DPG, diphosphatidylglycerol PP, phosphatidic acid phosphatase PE, phosphatidylethanolamine PC phosphatidylcholine PEMT, phosphatidylethanolamine A-methyltransferase CT, CTP phosphocholine cytidylyltransferase PS, phosphatidylserine CK/EK, choline/ethanolamine kinase CPT, CDP-choline 1,...

Instead of being dephosphorylated, phosphatidic acid can be converted to CDP-diacylglycerol. This reaction catalysed by phosphatidic acidiCTP cytidylyltransferase (EC 2.7.7.41), is important for the synthesis of the negatively charged phos-... 

---