Interaction of phospholipase A with an axon plasma membrane preparation.

The rates at which the phosphalipase A catalyzed inactivation of the axonal cholinergic binding macromolecule (ACBM), activation of acetylcholinesterase, and hydrolysis of fatty acid acyl esters were measured in an axon plasma membrane preparation from lobster nerves. The inactivation of ACBM was shown not to be caused by products of the reaction. The solubilized ACBM was also sensitive to phospholipase A inactivation. These results indicated a direct role for the phospholipid in the binding of cholinergic ligands to ACBM. It is suggested that ACBM may be a postsynaptic cholinergic receptor that is in a different lipid environment in the axon plasma membrane. A comparison with the effect of phospholipase A on axonal conduction in intact nerves suggests that the ACBM is directly involved in this process.