The invention relates to a method for the enzyme-catalysed hydrolysis of polyacrylic acid esters. According to the method, at least one polyacrylic acid ester is provided and incubated with at least one enzyme selected from enzymes (EC 3.1) acting on ester bindings, until the ester groups contained in the polyacrylic acid ester are partially or fully hydrolytically split, and optionally the modified polymer obtained thereby is isolated. The invention also relates to the enzymes used and mutants thereof, nucleic acids coding for the enzymes, vectors comprising the nucleic acids, micro-organisms comprising the vectors, and the use of the enzymes, the vectors or the micro-organisms for carrying out a method for the enzyme-catalysed hydrolysis of polyacrylic acid esters. The present application also relates to polymer reaction products that can be obtained by the method, and methods for producing esterases.