Abstract
Catalytic effects of galactose oxidase on the oxidation of β-
D-galactose-carrying lipids with an oligo-ethylene glycol spacer (number of ethylene glycol units (
n)=1, 2, 3, 6, 9, 13, and 20) were examined. The affinity of galactose oxidase for the galactose residue in the amphiphile (estimated by the inverse of the Michaelis constant,
K
m) was much higher than those for free
D-galactose and small β-
D-galactopyranosides, and dependent on the length of the ethylene glycol spacer. That is, both below and above the critical micellar concentration, the 1/
K
m values decreased with an increase in the
n value. The effectiveness of the enzyme, which can be estimated by the
k
cat/
K
m value, showed the same tendency as the 1/
K
m value. These results could be attributed to the role of the nonpolar environment around the galactose residue in the binding by the enzyme. A significant enhancement of the enzymatic oxidation of galactose residue on the liposome surface was also observed.