Biochemistry II: exam 4 (chapter 26) DRAFT

Phosphatidate synthesis

• addition of two fatty acids to glycerol 3-phosphate

• endoplasmic reticulum and outer mitochondrial membrane

• Uses acyl CoA

• Enzyme: glycerol phosphate acyltransferase

Phosphatidate synthesis: salvage pathway

• using DAG

• Enzyme: diacylglycerol kinase (requires ATP

Triacylglycerol synthesis from phosphatidate

• hydrolysis of phosphatidate yields DAG

  • enzyme: phosphatidic acid phosphatase (PAP; part of TAG synthetase complex)

• Acylation of DAG yields a TAG

  • enzyme: diglyceride acyltransferase (part of TAG synthetase complex)

  • Uses acyl coa

Pathway integration

Phospholipid biosynthesis

• takes place in ER

• Phosphatidate (or DAG) + alcohol = phospholipid

  • at least one of the starting materials must be activated

    • phosphatidate activation by CTP yields CDP-diaglycerol

      • CDP-diaglycerol can react with an alcohol to form a phospholipid

        • alcohol = inositol yields phosphatidylinositol + CMP

        • alcohol = phsphatidylglycerol yields cardiolipin (diphosphatidylglycerol) + CMP

          • cardiolipin is only found in mitochondrial membranes

    • In other cases, the alcohol is activated by phosphorylation then reacted with CTP to form the CDP-alcohol

      • ethanolamine gets phosphorylated to phosphorylethanolamine, then reacts with CTP to form CDP-ethanolamine. CDP-ethanolamine reacts with DAG to yield phosphatidylethanolamine

        • phosphatidylethanolamine can yield phosphatidylcholine (most common phospholipid) by methylating it with 3 S-adenosylmethionine (SAM) molecules

          • only when one is deficient in choline. If dietary choline is sufficient, then simply activation of the choline yields phosphatidycholine