Enzymes are proteins which catalyse the biochemical reactions in living cells. Chemically they are globular proteins secreted by cells to regulate their metabolic activities. The enzymatic reactions are very specific, i.e. a particular enzyme catalyses only a particular biochemical reaction, but not others.
The speed of the catalytic reaction depends on the temperature of the system, the pressure of the system, the concentration of the substrates, the concentration of the enzyme, the concentration of the enzyme-inhibitors and the concentration of the products in the reaction mixture.
Enzymes and broadly classified into two groups. They are intracellular enzymes and extracellular enzymes. The intracellular enzymes are produced in the cell; they catalyse the reactions within the cell itself. But the extracellular enzymes are secreted by cells and are transported to different sites to catalyse the biochemical reactions.
A wide class of organisms are used as process-organisms to extract enzymes in industries. These organisms include bacteria, fungi and actinomycetes and the cultures of plant and animal cells. They utilize the nutrients present in the culture medium and accumulate enzymes either in the cells or in the medium. The enzymes are isolated and put into many uses in industries.
The proper strain of microorganism must be selected for the industrial production of enzymes. The selected strain must have the following features, then only the isolation of a large amount of the desired enzyme from the spent medium will be possible.
• The organisms must accumulate the desired enzymes in the medium.
• They must produce a large proportion of desirable enzyme within a limited time.
• They must produce the desirable enzymes steadily.
• They must grow in cheap raw materials.
• They must be non-pathogenic organisms for producing the enzyme.
• They must adjust themselves to the physical and chemical properties of the culture medium such as temperature, pH, the availability of substrates, etc.
Generally microorganisms produce a small quantity of enzymes in the culture. Genetics of the microbes are manipulated properly in order to make them to produce enzymes in large amounts.
Mutation favours the enzyme production by avoiding the requirement of inducer molecule for the synthesis of enzymes. This type of mutation causes the production of more enzymes in the inducer-dependent enzyme synthesis. Some mutants show resistance to the repressor molecule during the enzyme biosynthesis.
Some mutation induce the production of more copies of the genes, responsible for the production of a particular enzyme. Point mutations are used for this purpose.
Some enzymes are produced in a large amount when the microbial culture is treated with some specific substances. Such substances which induce the production of specific enzyme in the microbes, are called inducers. The enzymes thus produced are named inducible enzymes. For example, starch is an inducer molecule which induces the cells of Bacillus sps to produce alpha- amylase (an enzyme).
Some enzymes are continuously produced by the organisms in the culture without any response to the addition of inducers to the culture. Such enzymes are called constitutive enzymes.
Sometimes the biosynthesis of enzyme is blocked by the addition of certain substances to the culture, This process is called repression. There are two types of repressions, namely feed back repression and catabolic repression.
In feed back repression, the end product of the biosynthetic pathway inhibits the further synthesis of the enzyme. For example, addition of sulphur containing amino acids inhibits the biosynthesis of protease in Bacilli.
In catabolic repression, the substrate molecules repress the biosynthesis of enzymes. The fact is generally used to block the synthesis of undesirable enzyme. For example, in E.coli, glucose galactosidase enzyme is repressed by the glucose present in the medium.
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