What is enzyme activity?

It is important to understand some basic terms about enzyme preparations that are frequently used in this industry. First things first, let us talk about enzyme activity, which is one of the most important technical specifications of enzyme preparations.

Enzyme activity, usually simply referred to as activity, means the ability of an enzyme that catalyzes a specific chemical reaction under certain conditions. It is expressed in terms of the activity unit (U), which is defined as the amount of the enzyme that catalyses the conversion of one micromole of substrate per minute under standard conditions, such as at a temperature of 25°C and the pH value and substrate concentration that yield the maximal substrate conversion rate. The higher the activity is, the stronger the catalytic ability of an enzyme preparation.

An enzyme preparation with higher activity will enable less dosage level in the industrial production process of its application, thus reduce the production cost. That is the reason why activity is of the most interest in enzyme preparation industry rather than other specifications. For example, as a concentrate enzyme preparation, the activity of Fungal Alpha-Amylase Boli FAA-420 is 56,000 U/ml, much higher than that of Fungal Alpha-Amylase Boli FAA-400 which has an activity of 28,000 U/ml. Given the same processing conditions in starch sugar production, the typical dosage level of Boli FAA-420 is within the range of 0.04 to0.25 kg per ton of dried substance, whilst that of Boli FAA-400 is from 0.075 to0.5 kg accordingly.

The definition of enzyme activity could be plausible in terms of the criteria of “standard conditions”, which usually refer to optimal conditions. However, these so-called optimal conditions, especially with regard to pH, ionic strength, temperature, substrate concentration, etc, could vary both between laboratories and between suppliers. They may also be dependant according to the particular application in which the enzyme is to be used. In addition, enzyme preparations of the same notional specific activity could be different with regard to stability and total catalytic productivity. Conditions for maximum initial activity may not necessarily be those for maximum stability. Great care has to be taken in the consideration of these factors when the most efficient catalyst for a particular purpose is to be chosen.

June 4, 2012Permalink 1 Comment

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