Abstract:

The effect of microwave treatment on the activity, stability, kinetic parameters and conformation of glucose isomerase
(GI) was studied. Results indicated that different periods and power levels of microwave treatment had different effects on GI
activity. After microwave treatment at powers of 300 W and 400 W for 5 min at 70 ℃, GI activity was increased by 14.23% and
8.42%, respectively. However, GI retained 95.69% and 90.78% of its original activity at 600 W and 800 W, respectively. The
microwave treatment also had effects on the optimal reaction temperature and kinetic parameters, but had scarce effects on the
optimal pH. Moreover, partial unfolding of GI and changes in microenvironment of tryptophan and tyrosine residues were observed
from the ultraviolet and fluorescence spectra of microwave-treated GI. Thus we further speculated that the tertiary structure of GI
was also disturbed by microwave treatment. As a conclusion, this study demonstrates that microwave treatment can change some
properties of GI presumably by changing its conformational structure.

Key words: glucose isomerase, microwave treatment, activity, optimal reaction temperature, optimal pH, conformation