The enzyme is thought to reduce the “path” of the reaction. This shortened path would require less energy for molecule of substrate converted to product. Given a total amount of available energy, more molecules of substrate would be converted when the enzyme is present than when it is absent. Hence, the reaction is said to go faster in a given period of time.
A theory to explain the catalytic action of enzymes was proposed by the Swedish chemist Savante Arrhenius in 1888, this theory is known as the lock and key theory and it uses the concept of an “active site.” At first it was thought that an enzyme’s active site was merely a negative impression of substrate. This idea was called ‘lock and key’ because the substrate seems to fit into the active site as a key fits into a lock.
The induced fit theory. The change in the active site brings the amino acids into the correct positions in the active site so a reaction can occur. (See diagram below.)
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This essay will now look at particular enzymes in industry and medicine.
An enzyme that is very important in the textile industry is amyloglucosidase, also known as glucoamylase. In the textile industry amylases are used to remove starch-based products for improved and uniform wet processing. The advantage of these enzymes is that they are specific for starch, removing it without damaging to the support fabric (e.g. cotton and its blends).
Glucoamylases are sensitive to temperature, being inactivated at temperatures above 60 ºC. However for this purpose this does not really affect its use. The optimum pH level of these enzymes is 4.0-4.5. This is important as if you know the optimum rate the enzyme functions quicker and then more of the product needed will be made quicker and therefore be able to be sold sooner.
Enzymes are increasingly used in the food industry one enzyme many people are grateful for is Chymosin. This is actually one of the few enzymes that are known to have been made from genetically engineered organisms. Chymosin, also known as Rennin, is a proteolytic enzyme synthesised by chief cells in the stomach. Its role in digestion is to curdle or coagulate milk in the stomach, a process of significant importance. If milk were not coagulated, it would rapidly flow through the stomach and miss the opportunity for initial digestion of its proteins.
However Chymosin is used in the food industry in cheese making. Chymosin efficiently converts liquid milk to a semisolid like cottage cheese, allowing it to be reserved for longer periods. Its does the same in the body allowing it to be reserved for longer periods in the stomach. In the body Chymosin secretion is maximal during the first few days after birth, and declines thereafter, replaced in effect by secretion of pepsin as the major gastric protease. Chymosin is also similar to pepsin in being most active in acidic environments, which makes sense considering its operation.
Chymosin’s structure consists of 323 amino acids in the polypeptide chain. The chain has three disulfide bridges. The molecule is kidney shaped and contains two domains. The folding pattern has pseudo 2-fold symmetry that is common for members of this acid proteinase family.
Enzymes in agriculture: the only major agricultural area to utilise enzymes is the feeding of monogastric animals. However, there are two applications, which currently utilise enzymes.
Biological silage inoculants frequently contain enzymes in addition to lactic acid bacteria. The enzymes in such products partially break down some of the cell wall components of the plant material to be ensiled into soluble sugars. These liberated sugars are then metabolised by the natural or applied lactic acid bacteria such as Lactobacilli or Pediococci into lactic acid, which reduces the pH and so ensiles the crop.
Some enzyme preparations have been reported to improve the utilisation of feeds for ruminant animals.
The uses of enzymes in arable agriculture especially in the processing of some major crops and in waste disposal systems are areas, which have not been fully investigated.
An enzyme in beer brewing essentially involves the production of alcohol by the action of yeasts on plant materials such as barley, maize, sorghum, hops and rice. The yeast cells are capable of converting simple sugars into alcohol and carbon dioxide. However, most of the sugar present in plant materials is in the form of complex polysaccharides such as starch and cannot be readily utilised. Traditionally these nutrients are "released" by the process of malting whereby barley is allowed to partly germinate during which endogenous enzymes are released which degrade starch and protein to simple sugars and amino acids which can be utilised by the yeast cells.
The malting process is a relatively expensive way of manufacturing enzymes and is not always easy to control. Industrial enzymes such as amylases, glucanases and proteases can be added to unmalted barley resulting in the same simple sugars and amino acids that malting would liberate but in a more controlled approach.
Enzymes also play an important role as filtration improvers. Slow filtration of the mash or final beer often results from the presence of viscous polysaccharides such as xylans and glucans. Pretreatment with xylanases or glucanases, break down these viscous polysaccharides thereby increasing filtration rates and preventing fouling of filtration membranes.
Enzymes have been used in the detergent industry, since the mid 1960’s and is probably the best-known application of industrial enzymes especially in laundry products - the so-called "biological" washing powders, liquids and tablets.
The main enzyme activity in biological laundry detergents is protease, which acts on organic, stains such as grass, blood, egg and human sweat. However, it has become more common in recent years to include a range of enzyme activities including lipases and amylases. Lipases are effective on stains resulting from fatty products such as oils and fats (and lipstick!) whilst amylases help remove starchy food deposits.
More recently, colour enhancing and "anti-bobbling" washing powders have been developed which contain cellulases. It is thought that the mode of action of such cellulases is to remove detached cellulose fibrils, which cause a progressive dulling of the colour as dirt is trapped on the rough surface of the fabric.
Enzymes have become particularly important in products developed for the pre-soaking or spot application onto laundry. In these cases soils are loosened by enzyme action prior to the main wash in a detergent. Such products result in reduced detergent costs and the ability to save energy by lower temperature washing.
The use of enzymes in automatic dishwashing detergents is also becoming popular. Typical enzyme activities are protease and amylase to remove food particles. Such new products are more environmentally friendly as they contain less bleaching agents and phosphates.
Enzymes are used in all areas of medicine ranging from diagnosis to treatment. Enzymology is a critical part of understanding the cause of diseases. Most genetic diseases are a result of a particular enzyme deficiency. It can often be difficult to find out about the uses of enzymes in medicine because the clinical diagnostics and pharmaceutical industries work behind tightly closed doors until they want to tell the general public about some positive discovery. Basically, the uses of enzymes in medicine include:
Analytical tests (for example, glucose is always measured by an enzyme based test utilising glucose oxidase) Diabetics use strips of paper impregnated with glucose oxidase to monitor their blood sugar. When a drop of blood is added to the strip, the glucose oxidase metabolises the glucose and a series of reactions produce a measurable colour change that is proportional to the amount of glucose.
The presence of enzymes where they should not be is also a vital diagnostic of disease. For example when the liver is diseased or damaged, enzymes only found normally in the liver leak into the bloodstream. Testing the blood for these activities therefore is used to confirm liver damage.
Therapeutic enzymes are actually used as medicines, usually to replace enzyme deficiencies in patients. An example is the use of blood clotting factors to treat haemophilia, or the opposite where proteases are used to degrade fibrin; use of proteases can prevent the formation of dangerous blood clots. The protease (peptidase) used in therapy of thromboembolic diseases is called a tissue plasminogen activator. Nuclease is considered as a possible therapy for cystic fibrosis, but it is not clear therapeutically how successful this has been.
Proteases are also used in wound therapy. In this case they are called deriding agents and are used to clean a wound so therefore speed up the healing process.
Some proteases are also used as anti-inflammatory reagents. An enzyme called superoxide dismutase is also available as an anti-inflammatory agent, but how successful it has been as a commercial product, is not clear.
Drug manufacture: The chemical synthesis of complex drugs is often difficult and companies frequently turn to enzymes to perform chemical conversions. In fact the company Chiroscience was set-up to investigate the use of enzymes in pharmaceutical manufacture.
In a semi-therapeutic way, enzymes are also used to aid digestion, both in humans and animals. In humans, enzymes are used to supplement the natural amylase, lipase and protease produced normally by the pancreas. Many ethnic groups also have a problem called lactose intolerance. This means, as these people get older they lose the enzyme lactase (converts lactose into glucose and galactose). This means they cannot ingest milk or dairy products. Lactase supplements help to avoid stomach upsets for these people.
In conclusion it is simple to see that life today as we know it, would be very different without enzymes, in fact it would be impossible as enzymes are used everyday by our bodies to perform what some may see as everyday functions. However in regards to industry and medicine, in particular, enzymes play a huge role. They are used in many of the treatments administered to patients and much more. They also play a major role in industry, becoming over the years a huge, huge market. Quite simply although they go unnoticed by many they are owned a great amount of gratitude and as a great immunologist Dr. Pavels Ivdra once said ‘Enzymes the unsung heroes’ (Medical Journal 1996).
Bibliography:
AS – A new introduction to Biology by Bill Indge, Martin Rowland and Margaret Baker – page 61
Collins Advanced Sciences Biology – Various authors
Medical journal Article – Dr. Pavels Ivdra – 1996
Biology For You – Gareth Williams
