Penetration of glucose oxidase and of the hydrophobically modified enzyme into phospholipid and cholesterol monolayers

The penetrant ability of the native glucose oxidase, GOx, and of the hydrophobically modified enzyme GO(mod) realized by grafting to its lysine residues alkyl C-16 chains, into phosphatidylcholine dibehenoyl (DBPC), phosphatidylcholine dipalmitoyl (DPPC), phosphatidyl-ethanolamine dipalmitoyl (DPPE), phosphatidylserine dipalmitoyl (DPPS), and cholesterol (CHOL) monolayers was assessed by surface pressure measurements at constant area by enzyme injection to the aqueous phase beneath spread monolayers, As revealed by the magnitude of surface pressure increments (Delta Pi), both the quantities and the rates of penetration of the enzymes into these monolayers were lipid chemical nature and enzyme concentration dependent, When compared with GOx, GO(mod) displayed an enhanced penetrant ability into all the studied monolayers that resulted in rapidly attained Delta Pi plateau values, characteristic of stable systems. The influence of lipid hydrocarbon chain length and of the polar headgroup charge on the efficiency and effectiveness of GOx and GO(mod) penetration into these monolayers is discussed. (C) 1999 Academic Press.