Differential hydrolysis of immobilized phosphatidylcholines by phospholipases A2 and C.

A novel phospholipid, 1-fatty acyl-2-(12-aminododecyl) phosphatidylcholine (APC), was synthesized and reacted with two different activated agarose matrices, differing in the spacer arm length: N-hydroxysuccinimidylester agarose (1-atom spacer arm) and N-hydroxysuccinimidylester-6-aminohexanoic acid agarose (8-atom spacer arm). Both immobilized phosphatidylcholines were readily degraded by Bacillus cereus phospholipase C at similar rates. By contrast, Crotalus adamanteus phospholipase A2 hydrolyzed long-spacer arm phosphatidylcholine, but had less than one tenth of the activity towards the short-spacer arm one. These results are interpreted in terms of a chain length-related steric hindrance caused by the matrix, affecting phospholipase A2 but not phospholipase C activity, supporting the view that the first involves a deeper burrowing of the substrate into the enzyme molecule.