Enzymes

Enzymes are biological catalysts, speeding up the chemical reactions in living organisms.
They are protein molecules which are composed of long chains of amino acids.
These molecules create a specific shape with an area, the active site, where substrates can bind.
The substrate must have a specific geometric shape that fits the active site for the reaction to occur, a concept known as the lock and key theory.
Upon binding, the substrate-enzyme complex is formed, and the reactive conditions are set for the reaction to take place.
The product formed from the reaction is released and the enzyme is free to act again on more substrate molecules, implying that enzymes are not used up in reactions.
Enzymes are highly specific due to their complex 3D shape formed from the sequence of amino acids. This property is called enzyme specificity.
Enzymes can be denatured by extreme conditions or pH, which disrupts the protein structure and the active site, rendering the enzyme inactive.

Factors Influencing Enzyme Activity

The rate of enzyme-controlled reactions depends on enzyme and substrate concentrations, temperature, pH and the presence of inhibitors or activators.
Increasing the temperature increases the kinetic energy of the molecules, thus increasing the rate of reaction until the optimum temperature where the enzymes work best. Beyond this, the enzymes denature and the rate decreases.
Each enzyme has an optimal pH level at which it can perform its function most efficiently. Deviation from this optimal pH can slow down the reaction or denature the enzyme.
Enzyme concentration and substrate concentration influence the rate of reactions - if all other factors are constant, the higher the concentration, the faster the reaction rate.
Enzyme inhibitors are substances that directly or indirectly interfere with the functioning of the enzyme. They can be competitive (compete with the substrate for the active site) or non-competitive (bind to the enzyme causing a change in its shape).

Industries take advantage of the properties of enzymes, especially their specificity and efficiency. These applications range from food processing, detergent manufacturing, to medical and scientific research.
For instance, proteases are used in biological washing powders to break down protein stains, and in the food industry to tenderise meat.
Amylases are used in brewing and distilling industries to convert starch to sugar, and pectinases are used in fruit juice extraction to break down pectin.
Some enzymes like restriction enzymes are used in genetic engineering to cut DNA at specific sites, while ligases are used to join pieces of DNA together.