Enzyme Peroxidase Lab Report

Discussion
In this experiment the enzyme peroxidase and the substrate hydrogen peroxide were not mixed initially, instead they were both placed in separate tubes and were incubated at a specific temperature, to prevent hydrogen peroxide from undergoing any reaction with peroxidase until they both acquire the required temperature.
The results of this experiment showed a specific pattern. As the temperature increased, the absorbance recorded by the spectrophotometer increased indicating that the activity of peroxidase enzyme has increased.At 4C the absorbance was low indicating a low peroxidase activity or reaction rate. At 23C the absorbance increased indicating an increase in peroxidase activity. At 32C the absorbance reached its maximum indicating that peroxidase activity reached its highest value and so 32 C could be considered as the optimum temperature of peroxidase enzyme. Yet as the temperature increased up to 60C, the absorbance decreased greatly indicating that peroxidase activity has decreased. This happened because at low temperature such as 4 C the kinetic energy of both enzyme and substrate molecules was low so they moved very slowly, collided less frequently and formed less enzyme-substrate complexes and so little or no products. Yet, at 23 C, as the temperature increased, enzyme and substrate molecules

gained more kinetic energy, moved faster, collided more frequently and formed more enzyme-substrate complexes and more products [Danson MJ 2007]. Also, as the temperature increased further up to 32 C the enzyme and substrate molecules gained much more kinetic energy, moved faster, collided more frequently and formed more enzyme-substrate complexes and more products. But as the temperature went up to 60C the enzyme and substrate molecules gained much more kinetic energy that caused them to vibrate rapidly until the hydrogen bonds that maintain the tertiary structure of the active site of the enzyme peroxidase broke down.This changed the shape of the active site so the substrate was no longer able to fit into it precisely and thus enzyme-substrate complexes did not form and the reaction rate decreased till it almost became zero and so the reaction stopped. In other words, the enzyme peroxidase has been denatured.
By looking at the graph in Figure 1 it can be easily observed that the rate of the reaction at 60  C and the rate of the recovery reaction are almost the same, both are equal to zero.

This indicated that the effect of high temperature on the activity of peroxidase was irreversible and so if the optimum temperature was restored the enzyme activity will not increase again because denaturation resulted in a permanent change in the shape of the active site of the peroxidase enzyme. In conclusion, the results of this experiment supported the hypothesis that enzymes including peroxidase enzyme are sensitive to temperature changes[George

N.1969].