Selenization of ovalbumin by dry-heating in the presence of selenite: effect on protein structure and antioxidant activity.

Ovalbumin (OVA) was selenized by dry-heating in the presence of selenite, and the structural characteristics and improved antioxidant activity of selenized OVA (Se-OVA) were investigated. Although the change of the secondary structure in the OVA molecule by selenization was small, the enthalpy change for denaturation and tryptophan fluorescence intensity of OVA decreased greatly by selenization. The digestibility of OVA was significantly improved by selenization. The results all together demonstrated that molten globule conformation of OVA was formed by selenization. Some selenized tryptic peptides from Se-OVA were identified by MALDI-TOF-MS. Remarkably, the antioxidant activity of OVA was improved when selenite was conjugated compared with free selenite. These results indicate that the enhanced antioxidant activity of Se-OVA is ascribed to the conjugated Se and the formation of a molten globule conformation of protein.