Difference Between Enzyme Activity and Specific Activity

The key difference between enzyme activity and specific activity is that the enzyme activity refers to the amount of substrates converted to products per unit time while the specific activity of an enzyme refers to the activity of an enzyme per milligram of protein.

Most enzymes are protein molecules. They are biocatalysts and aid biological functions. Enzymes act by increasing the rate of reaction of biochemical reactions. Furthermore, they have specific 3D shapes that facilitate their function. Also, in enzyme kinetics, the behaviour of the enzyme can be expressed in two main measurements. They are the Enzyme Activity and the Specific Activity of the enzyme.

CONTENTS

1. Overview and Key Difference
2. What is Enzyme Activity
3. What is Specific Activity
4. Similarities Between Enzyme Activity and Specific Activity
5. Side by Side Comparison – Enzyme Activity vs Specific Activity in Tabular Form
6. Summary

What is Enzyme Activity?

Enzyme activity defines as the number of moles of substrate converted to products per unit time. Therefore, the enzyme activity measures the number of active enzyme moles present in the reaction. However, this measurement depends on many factors such as the temperate, pH, substrate concentration, enzyme concentration, presence of inhibitors and the presence of activators, etc. When the factors affecting the enzyme activity is optimal, the rate of the enzyme reaction is high. Therefore, it is important to maintain optimal conditions for the enzyme activity to be at its optimal.

In general conditions, the increased concentrations of substrates and enzyme may increase the activity of the enzyme. Furthermore, the presence of inhibitors can retard the enzyme activity. In contrast, the presence of activations such as divalent ions may induce the reaction while increasing the activity of the enzyme. The SI unit of enzyme activity is katal. But, due to the practical constraints, the commonly used unit is the Enzyme Unit (U) which is equal to 1 μmol min^-1. Therefore, the enzyme units suggest the activity.

What is Specific Activity?

The specific activity of an enzyme defines the purity of an enzyme in a protein mixture. It measures the activity of an enzyme in one milligram of total protein. Hence, this unit is especially important in the purification of enzymes from proteins, in order to assess the purity of the enzyme. Furthermore, the specific activity is measured by the number of products formed in unit time under specific conditions, per milligram of total proteins.

Moreover, the specific activity of an enzyme depends on the biochemical nature of the enzyme and the intermolecular interactions of the enzymes and the surrounding proteins. The SI unit of specific activity is katal kg^-1. But, due to the practical constraints associated with this unit, it expresses as μmol mg^-1 min^-1. Furthermore, the specific activity of an enzyme also measures the turnover number of the enzyme.

What are the Similarities Between Enzyme Activity and Specific Activity?

• Enzyme Activity and Specific Activity are two measurements that assess the ability of the enzyme to convert substrates to products per unit time.
• The unit of both these is katal.
• Both are dependent on the substrate and enzyme concentrations.

What is the Difference Between Enzyme Activity and Specific Activity?

In enzyme kinetics, enzyme activity and specific activity are two important measurements. Enzyme activity measures the rate of substrates converting into products while specific activity measures the activity of an enzyme in one milligram of total protein. Hence, this is the key difference between enzyme activity and specific activity. Furthermore, there is another difference between enzyme activity and specific activity based on the additional use of the specific activity. That is, the specific activity can describe the purity of the enzyme as well.

Summary – Enzyme Activity vs Specific Activity

Enzymes are a vital component in all biochemical reactions. And the efficiency of an enzyme is dependent on its activity. Hence, enzyme activity is the rate at which substrates are converted to products. This implies the efficiency of the enzyme. In contrast, the specific activity is a type of enzyme activity. This signifies the purity of an enzyme per milligram of protein. Nevertheless, both measurements help to analyze the kinetic behaviour of the enzyme. Hence, this is the difference between enzyme activity and specific activity.

Reference:

1.Phillips, Theresa. “Why Specific Activity Is Important to Know When Purchasing Enzymes.” The Balance Small Business, The Balance. Available here 

Image Courtesy:

1.”Enzyme high pressure b”By Wladimir Labeikovsky – Flickr, (CC BY-SA 2.0) via Commons Wikimedia