Figure 4. Immunoreactivity by ELISA.

The antibody concentration required to achieve 50% maximum ELISA signal (EC₅₀) was determined for each enzyme using polyclonal anti-A1-III antibody purified from rabbit immune serum. The results are reported as fractional immunoreactivity based on normalization with the WT-his enzyme, which was included as an internal control in all experiments (see Experimental Procedures). All of the PEGylated enzymes were found to exhibit significantly reduced antibody binding relative to the WT-his control (p<0.01 for each). Error bars represent standard deviation.