Studies on the activity of phospholipase D with alkyl phosphorylcholines

The activity of phospholipase D from the Savoy cabbage on alkyl phosphorylcholines containing alkyl groups of C14 to C22 was examined. Apparent Km and maximal velocity values in the presence of diethyl ester were 3.6-8.3 mM and 0.14-0.29 mumol/(min.mg protein), respectively. The maximal velocities for alkyl phosphorylcholine homologues were lower than the value for pig phosphatidylcholines, but higher than those for lysophosphatidylcholines and synthetic phosphatidylcholine with saturated acyl chains. Results suggest that solubilities of the substrates in the organic solvent play an important role in activity observed with phospholipase D.