Hydrolysis of phenolic glycosides by midgut β-glucosidases in Papilio glaucus subspecies

Abstract

β-1,4-glucosidase (EC 3.2.1.21) activity toward several phenolic glycosides characteristic of the Salicaceae was examined in subspecies of the eastern tiger swallowtail, Papilio glaucus. Midgut β-glucosidase activity of larval Papilio glaucus canadensis, which are adapted to phenolic glycosides, was one-third to one-half that of Papilio glaucus glaucus, which are unadapted to phenolic glycosides. Both subspecies hydrolyzed the phenolic glycoside salicin much more rapidly than the salicin derivative salicortin, but activity against even that substrate was high in comparison to β-glucosidase activity in other lepidopteran species. Ingestion of phenolic glycosides for 2 days prior to dissection suppressed β-glucosidase activity in P. g. canadensis, but induced activity in P. g. glaucus. β-Glucosidase activity varied among larvae fed different host plant species, and across seasons within a species, in P. g. glaucus.