User:Phaeton68/sandbox

Biosynthesis of Plasmalogen (PLs)
Biosynthesis of plasmalogens begins with association of peroxisomal matrix enzymes GNPAT (glycerone phosphate acyl transferase) and AGPS (alkyl-glycerone phosphate synthase) on the luminal side of the membrane. These two enzymes can physically interact with each other to increase efficiency. Therefore fibroblasts without AGPS activity have a reduced GNPAT level and activity.

GNAPT catalyzes the first step which is the acylation of DHAP at the sn-1 position.This is followed by the exchange of the acyl group for an alkyl group by AGPS. . The 1-alkyl-DHAP is reduced to 1-O-alkyl-2-hydroxy-sn-glycerophosphate (GPA) by an acyl/alkyl-DHAP reductase located in both peroxisomal and Endoplasmatic Reticulum (ER) membranes. All other modifications occur in the ER. First an acyl group is placed at the sn-2 position by an alkyl/acyl GPA acyltransferase and the phosphate group is removed by a phosphatidic acid phosphatase to form 1-O-alkyl-2-acyl-sn-glycerol. Together with CDP-ethanolamine a phosphotransferase forms 1-O-alkyl-2-acyl-sn-GPEtn. After dehydrogenation at the 1- and 2-positions of the alkyl group by an electron transport system and plasmenylethanolamine desaturase the vinyl ether bond of plasmalogens is finally formed. Plasmenylcholine is formed from 1-O-alkyl-2-acyl-sn-glycerol by choline phosphotransferase. As there is no plasmenylcholine desaturase choline plasmalogens can be formed only after hydrolysis of ethanolamine PLs to 1-O-(1Z-alkenyl)-2-acyl-sn-glycerol that can be modified by choline phosphotransferase and CDP choline.

