Phospholipid interactions with a xylosyl-transferase from aortic wall

Abstract In aortic wall a xylosyltransferase catalyzes the transfer of [ 14 C]-xylose from UDP-[ 14 C]-xylose onto endogenous or exogenous acceptor (poly-L-serine). The purification of this enzyme is carried out by hydrophobic chromatography onto an octyl-agarose column which conducts to the separation of the endogenous acceptor from the enzyme. The xylosyltransferase is markedly inhibited by phospholipids such as phosphatidic acid, phosphatidyl-L-serine and lysophosphatidylcholine. Our investigations upon synthetic phospholipids or analogs allow us to show that this change in enzymatic activity is ceither stereospecific nor dependent on the steric hindrance of phospholipidic compounds but is related to their polar headgroups, particularly to acidic groups of phosphatidylserine or phosphatidic acid. Detergents ionic or not interfere also as inhibitors. Exogenous phospholipids certainly induce some modifications in the enzymatic environment which could either lead to an enzymatic conformation change by preventing its aggregation or could interfere directly on the xylosyltranferase activity.