Enzymes are protein molecules that act as catalysts for many chemical reactions. Enzymes are very specific. The shape of the enzyme has to be just right; if the shape of the molecule is deformed even slightly it will not function. Enzymes bind to their substrate only; this makes them specific. This means they can be used to identify a specific substance in a sample. Enzymes are also very effective at low concentrations and work at moderate temperatures and pH that can help to reduce costs.
Enzymes are also biodegradable which means no waste is produced which would cost money to dispose of. It is for these reasons that they have a wide variety of commercial and medical uses. Enzymes that are used in medicine and industry are preferably grown by microbes. This is because microbes have a high growth rate; they are grown easily in bulk in fermenters. They have simple nutritional requirements and produce many extracellular enzymes which are easier to recover and purify.
The use of enzymes in medicine.
Enzymes have many uses in medicine. Streptokinase helps to dissolve blood clots which limits the chance of a further heart attack. In addition, Urokinase removes blood clots, for example in heart disease by breaking down the blood clots. The source of this enzyme is in human urine.
The enzyme glucose oxidase tests for blood glucose, for example in diabetes. The source of this enzyme is from fungi. Diastix are strips of cellulose that have the enzyme glucose oxidase stuck to one end. When dipped into urine containing glucose the reaction produces hydrogen peroxide. This reacts with another compound to give a colour change. The extent of the colour change will indicate the amount of glucose present.
L-asparginase is an enzyme which removes L-asparagine. L-asparagine is needed for the growth of tumours. Chemotherapy treatment for cancer uses L-asparginase, especially in leukaemia (cancer of the blood). This enzyme can be found in bacteria (E.coli).
Enzymes also have many roles in the pharmaceutical industry. Enzymes can be used as direct pharmaceutical products such as the treatment of genetic disorders which lead to a deficiency of a specific enzyme, or in the research and development of new drugs. They can be used to extract medicinally important compounds such as heparin – which thins the blood and stops it from clotting. Enzymes can also be used to remove chemicals such as hydrogen peroxide. Catalase removes hydrogen peroxide used to sterilise contact lenses. Enzymes can also be used in the field of molecular biology where almost all the processes of nucleic acid manipulation are preformed with enzymes.
1. Geneticists use restriction enzymes to isolate a segment of DNA that contains a gene of interest, for example, the gene that regulates the production of insulin.
2. A plasmid is extracted from its bacteria cell and treated with the same restriction enzyme can hybridize with this fragment’s “sticky” ends of corresponding DNA.
3. The hybrid plasmid replicates as part of the cell’s DNA when it is reincorporated into the bacterial cell.
4. A large number of daughter cells can be cultured and their gene products extracted for human use.
Enzymes can be used to aid digestion in both humans and animals. In humans, enzymes can be used to supplement the natural amylase, lipase and protease produced normally in the pancreas. Some people have a problem known as lactose intolerance. This means that as these people get older they lose the enzyme lactase (which converts lactose into glucose and galactose). This results in them being unable to digest milk or dairy products. Lactase supplements help to avoid stomach upsets for these people.
Proteases are also used in wound therapy. They are called debriding agents and are used to clean a wound, which accelerates the healing process. Some proteases are also used as anti-inflammatory reagents. An example of an enzyme that acts as an anti-inflammatory agent is ‘super oxide dismutase.’ Medically it does its job but how successful it has been as a commercial product is not yet clear.
The use of enzymes in industry
Enzymes have many uses in many industries, such as in the leather industry, in agriculture, in detergents, in the brewing of beer and in food processing.
The leather industry uses proteolytic and lipolytic enzyme in leather processing. These enzymes are used because they are closely associated with the structure of the animals’ skin. Alkaline proteases are added in the soaking phase. This reduces the processing time as well as removing dirt and fats. The next stage is dehairing and dewooling, enzymes are used to assist the alkaline chemical process. This improves the quality of the leather producing a cleaner and stronger surface, and softer leather. The next stage is bating which aims at deliming of collagen. In this phase, the protein is partly degraded to make the leather soft and easier to dye.
Enzymes can be used in agriculture to produce biological silage where enzymes partially breakdown some of the cell wall components of the plant material into soluble sugars. Theses sugars are then metabolised by the natural or applied lactic acid bacteria such as Lactobacilli or Pediococci into lactic acid. This reduces the pH and so improves the crop. Enzymes can also be used to help improve animal feed. The first commercial success was the addition of beta-glucanase into barley based animal feed. Barley contains beta-glucan, which causes high viscosity in the chicken gut. The addition of the enzyme improved the viscosity. Over 90% of animal feed is supplemented with enzymes to resolve this problem. Xylanase enzymes are also added to animal feed containing wheat. The addition of the enzyme increases the energy available to metabolise by 7-10% in various studies.
Detergents were the first large scale application for microbial enzymes. Biological detergents are products such as biological washing and dishwasher powders. The link between the two is that they both contain a range of hydrolysing enzymes. These include:
* Amylase, which breaks down starch stains.
* Cellulase, which breaks down the ends of damaged cotton fibres to remove the ‘bobbly bits’, produced during washing.
* Lipase, which breaks down lipid, stains into fatty acids and glycerol.
* Proteases, which break down many different proteins, found in food stains.
Enzymes can be used in the pulp and paper industry. The major application here is the use of xylanases in pulp bleaching. Xylanases ‘free’ lignin fragments by hydrolysing residual xylan. This reduces considerably the need for chlorine based bleaching chemicals.
Enzymes can be used in the starch industry. The treatment of starch with enzymes results in a variety of sweet syrups used throughout the food and beverage industries.
Enzymes can be used in the process of brewing beer. This includes the production of alcohol by the action of yeast on plant materials such as barley, maize, sorghum, hop and rice. The yeast cells are capable of converting simple sugars into alcohol and carbon dioxide. Most sugars in plants are in the form of complex polysaccharides such as starch and cannot easily be utilised. The enzyme that can be used in this process is amyloglucosidase.
Another application of enzymes is in the extraction of fruit juices. Crushing fruit such as apples releases a juice that is a valuable food product. An enzyme can aid extraction of the juice.
* Insoluble pectin causes plant cell wall to attach to adjacent cells.
* During storage, this pectin changes to a soluble form which binds water strongly.
* Pectinase is used to break down the pectin chains which reduces its water holding capacity.
* After pectinase treatment, crushing releases a greater yield of juice.
* The pectinase even clears the juice of ‘cloudiness’ caused by pectin.
Enzymes can be used also during food processing. Enzymes can be used to modify raw materials and aid in the processing or cooking stages. The roles of enzymes include,
* Enhancement of flavour,
* Enhancement of aroma,
* Removal of unwanted flavours and taints,
* Enhancement of digestibility,
* Modification of texture to aid processing and final product appearance,
* Upgrading raw materials
The main enzyme activity utilised in food processing applications is protease. However, applications utilising lipases and carbohydrate degrading activities are also becoming increasingly popular.
Enzymes are used in cheese making. Rennet is responsible for curd production from milk; many flavours in cheeses are a result of protease action. Lipase can help blue cheeses ripen from mould, e.g. Penicillium roquefortii. This can be done by using extracellular lipases.
Other example of how enzymes can be used in the food industry is listed below;
* Production of infant milk formulas from cow’s milk.
* Soy sauce production
* Production of hydrolysed vegetable protein
* Gelatin hydrolysis
* Production of meat extracts
* Cellulase is often used to soften vegetables.
* Proteases can be used as a meat tenderiser. This is why a piece of pineapple is often placed on top of a gammon steak – pineapple contains proteases.
Soft centres inside chocolates are possible because of the action of an enzyme. To start, the centre is solid and contains a polysaccharide and an enzyme. Once the chocolate coating has set, the enzyme breaks down the polysaccharide filling. This process turns the hard centre into the familiar soft and runny centre.
Enzymes such as proteases are used in the baking industry to lower the protein content of flour for biscuit production. Enzymes are also used in bread making. One of the ingredients of bread is yeast. After the dough has been kneaded, it is put in a warm place. The yeast respires with oxygen by feeding on the sugars and breaking them down into carbon dioxide and water. These gases cause the dough to rise. As the dough is baked the yeast is killed, and the gases continue to expand to give the bread a spongy texture. If dough without yeast is used then it will not rise.
In conclusion, life with out enzymes would be impossible. Enzymes are involved in almost everything around us and even inside us, people do not realise what a major part they play in our lives, without them life as we know it would not exist. As a great immunologist Dr. Pavels Ivdra once said, ‘Enzymes the unsung heroes’ (Medical Journal 1996).