methods for use of a multi - arm polyethylene glycol modifier in modification of asparaginase . the described multi - arm peg modifier enhances the subunit interaction of a multimeric protein to maintain the multimeric protein in a polymerized form , thereby improving the stability of the multimeric protein , maintaining the bioactivity of the multimeric protein , and reducing the probability of exposure of the antigen binding site after depolymerization of the subunits , so as to reduce the immunogenicity .