Polyethylene glycol-modified enzymes trap water on their surface and exert enzymic activity in organic solvents

Summary

Polyethylene glycol-modified enzymes dissolved and had high enzymic activity in organic solvents. A trace amount of water was found to be necessary for the activity. It was reasoned that the amphipathic polymer covalently attached to enzymes kept water molecules around them. This was supported by findings that : (1) high enzymic activity was found in water- immiscible solvents, whereas activity was never observed in water-miscible solvents; (2) enzymic activity was inhibited by increasing the concentration of dimethyl sulfoxide in benzene; (3) activity of lipase was inhibited by a water-miscible alcohol substrate, but was steadily elevated by increasing the concentration of a water-immiscible alcohol substrate; (4) water was not absorbed from benzene solution containing a modified enzyme by molecular sieves, while it was easily absorbed in the presence of a water-miscible organic solvent, dimethyl sulfoxide.