Lipase from Pseudomonas sp. was modified with the new amphipathic polymer poly(acryloymorpholine) - succinimidyl ester. The lipase derivative, which carried about 4.5 polymer chains per enzyme molecule, retained 54% of the original activity and showed a single symmetrical peak in gel filtration chromatography. The derivative displayed high transesterification activity in several chlorinated solvents. Compared to methoxypoly(ethylen glycol)-modified lipase, it showed lower solubility but better catalytic properties in organic media.