Properties and topology of enzymes methylating phosphatidylethanolamine to phosphatidylcholine in sarcoplasmic reticulum.
1. The synthesis of phosphatidylcholine (PC) by stepwise methylation of phosphatidylethanolamine (PE) is carried out by two enzymes in sarcoplasmic reticulum (SR) membrane of rabbit fast-twitch skeletal muscles. 2. Two methyltransferases (Met I and Met II) have a different pH optimum and affinity for methyl donor--S-adenosyl-L-methionine (SAM). 3. Met I is an integral SR membrane protein which active site faces the cytoplasmic surface of the membrane. 4. Met II is a peripheral, loosely bound protein, localized mainly on the extracytoplasmic (luminal) part of the SR membrane.
D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000201:enzymology; D003593:Cytoplasm / Q000201:enzymology; D007700:Kinetics; D008780:Methyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D009132:Muscles / Q000201:enzymology*; D050918:Phosphatidylethanolamine N-Methyltransferase; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*
D008780:Methyltransferases; D050918:Phosphatidylethanolamine N-Methyltransferase