Enzymatic determination of Catechol oxidase and Protease from fruits (orange, apple) and vegetables (carrot, tomato)

Abstract

The metabolic changes observed in any physical characters of fruits such as softness or colour change may be a result of changes in the activity of enzymes. The activity of plant polyphenoloxidases can cause enzymatic browning of fruits and vegetables and render food unfit for consumption due to formation of benzoquinone. Proteases degrade polypeptides and facilitate seed germination, leaf senescence, storage and release of amino acids for transport to actively growing regions. Kinetic activity is significant in understanding the process of fruit and vegetable ripening. It is evident from the literature that these enzymes (Catechol oxidase and Protease) have a prominent role in the immunity and defence mechanism. The present study has been focused on the enzymatic profiles of Catechol oxidase and Protease in fruits (Orange and Apple) and vegetables (Tomato and Carrot) which can be helpful in isolating and characterizing the enzymes from the above sources. Catechol oxidase and Protease were assayed using catechol and egg albumin as substrates, respectively. The Catechol oxidase activity was determined by measuring the change in colour of solution comprising of substrate and fruit/ vegetable extract due to formation of chromophoric substance, benzoquinone. Protease was assayed by measuring the rate at which the solution of egg albumin got digested by the activity of enzyme present in fruit/ vegetable juice. An increase in the absorbance due to formation of benzoquinone was observed in tomato, orange and apple juices due to increased activity on enzyme Catechol oxidase implying to more ripening of fruits/ vegetables as compared to carrot juice where the absorbance value was found to decrease indicating less enzyme activity. Protease enzyme activity in tomato juice was found to decrease due to increase in absorbance as lesser amount of egg albumin was digested by the enzyme. However Protease activity was found to increase in orange juice sample. From these results it is evident that, protease has a significant and prominent role in ripening and softening of the fruit (orange) as compared to vegetable (tomato).