Characterization of an Avian Protease Inhibitor

Background: Ovomucoid is a serine proteinase inhibitor in the egg whites of all avian species at a concentration of about 10 mg/ml. The involvement of proteinases in a multitude of control functions in an organism has created an interest in their physiological inhibitors. Regulation of proteolytic activity in tissues is a critical requirement in the maintenance of homeostasis. Egg white proteins possess ACE-inhibitory activity, & also high radical-scavenging activity. The combined antioxidant and ACE-inhibitory properties of egg white hydrolysates, or the corresponding peptides, would make a useful multifunctional preparation for the control of cardiovascular diseases. Proteases play key roles in several physiological processes, including intracellular protein degradation, bone remodeling, and antigen presentation, and their activities are increased in pathophysiological conditions such as cancer metastasis and inflammation. They are also required for invasion by microorganism. Four protease inhibitors have been identified in egg white: cystatin, ovomucoid, ovomacroglobulin (also known as ovostatin), and ovoinhibitor. Use of proteinase inhibitors in the treatment of certain diseases has renewed interest in their specificity and stability, both of which in turn depend on the tertiary structure of the inhibitor. Structural alteration to obtain molecules of desired properties requires knowledge of relationship between structure, function and stability.
Aims: In view of its importance, in the present study duck ovomucoid was isolated and characterized for its physicochemical properties.
Methodology: Duck ovomucoid was isolated and characterized for its physicochemical properties. Analytical gel filtration (Sephacryl S-100 HR column) was used for purification, determination of molecular weight (MW), carbohydrate content and Stokes radius.
Results & Conclusion: The fluorescence emission spectrum was 302 nm, comparable to that reported earlier. Stokes radius was found to be 2.91nm the value was comparable with white leghorn hen (stokes’ radius 3.15nm). The extraordinary large value of stokes radius can be attributed to its high carbohydrate content which increases the hydration of the molecule. The inhibitor had the molecular weight of 29,300 and the carbohydrate content was 22%, the specific extinction coefficient of duck ovomucoid was found to be 5.82 at 279 nm and the stokes radius was 2.91nm.