Differential binding of phenothiazine urea derivatives to wild-type human cholinesterases and butyrylcholinesterase mutants

Most phenothiazine urea derivatives are specific butyrylcholinesterase inhibitors. Aminourea derivatives inhibit both acetylcholinesterase and butyrylcholinesterase and the use of butyrylcholinesterase mutants and elevated substrate reveals involvement of a salt linkage in that inhibitory process. A series of N-10 urea derivatives of phenothiazine was synthesized and each compound was evaluated for its ability to inhibit human cholinesterases. Most were specific inhibitors of BuChE. However, the potent inhibitory effects on both cholinesterases of one sub-class, the cationic aminoureas, provide an additional binding mechanism to cholinesterases for these compounds. The comparative effects of aminoureas on wild-type BuChE and several BuChE mutants indicate a binding process involving salt linkage with the aspartate of the cholinesterase peripheral anionic site. The effect of such compounds on cholinesterase activity at high substrate concentration supports ionic interaction of aminoureas at the peripheral anionic site.