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Protease assay

Protease assay

In certain fruits, such as pineapples and mangoes, the flesh contains protein-digesting enzymes (proteases). These may play a part in helping to soften the fruit tissues as the fruit ripens, making it even more attractive to animals that might disperse the seeds. So perhaps the activities of these proteases enzymes will increase during the ripening process.

Applications of plant proteases, such as ‘bromelain’ from the stems and fruits of pineapples, include uses in the pharmaceutical industry as a blood anti-coagulant, and in the prevention of proteinaceous hazes in chill-proof beers!

The assay

Protease enzymes are added to a milky colloidal suspension of egg albumen. As the protease enzymes digest the suspended particles of proteins, the mixture becomes more transparent. The absorbance changes in the reaction mixture are followed with a colorimeter. The protease content, for example in extracts of fruits, can be assayed by measuring the rate at which the solution of egg albumen and extract becomes clearer.

Preparation of the egg albumen colloidal suspension (enzyme substrate)

Carrying out the reaction

Ideas for investigations with this system (with fruits and vegetables)

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