Abstract:

Objective: To modify purified wheat esterase with dextran and methoxy polyethyleneglycol (mPEG), and characterize
the modified enzymes. Methods: Dextran and mPEG were activated by sodium periodate and trimer cyanuric chloride, respectively,
before being used to prepare the modified wheat esterases. Changes in the active groups in the modified enzyme molecules
were described through infrared spectroscopy, and their kinetic parameters and the effects of temperature and pH on the modified
enzyme activities were investigated. Results: In comparison with the native enzyme, the modified enzyme had better affinity for the substrate
alpha-naphthyl acetate, and retained the majority of enzyme activity. The residual activity of dextran-modified enzyme was 67.1%,
and the mPEG modified enzyme retained 87.7% of the original activity. In addition, thermal stability and acid-base stability of the two
modified enzymes were better than those of the native one, and the optimal pH of the mPEG-modified enzyme was changed. Conclusion:
The modified enzymes have more stability than the native enzyme and thus are of important practical significance.

Key words: wheat esterase, dextran, methoxy polyethyleneglycol, enzyme activity, stability