ACTION OF ALPHA-L-FUCOSIDE FROM OCTOPUS-VULGARIS HEPATOPANCREAS ON PHOSPHOLIPID-VESICLES CONTAINING THE FUCOSYLATED GANGLIOSIDE FUCGM1

The behaviour of a highly purified alpha-L-fucosidase (E.C. 3.2.1.51) extracted from octopus hepatopancreas was studied with phospholipid ve sicles composed of phosphatidylcholine (PC) and phosphatidylserine (PS ) containing the fucosylated ganglioside FucGM1, a potential natural s ubstrate of the enzyme. The substrate recognition and hydrolysis take place only with PS/FucGM1 mixtures via an association process of the e nzyme with the vesicles at acidic pH; the enzyme rapidly and stably bi nds to PS vesicles but not to PC vesicles. The data suggest that only the PS-associated enzyme is able to hydrolyse FucGM1 embedded in the s ame bilayer. The enzyme association with FucGM1/PS vesicles is a prere quisite for ganglioside hydrolysis but is followed by irreversible enz yme inactivation.