Enzymes in agriculture.

During dough formation a portion of the starch is degraded by endogenous wheat -amylase to maltose, which is utilised by the yeast to form carbon dioxide, which causes the dough to rise. However, the amount of degradation is very limited and can be increased by the addition of -amylase. The choice of amylase is very important as excessive starch hydrolysis results in poor loaf characteristics. Staling is thought to be caused by changes to starch during storage. Use of -amylase can help to prolong freshness.

Wheat is favoured for bread making because the protein fraction in wheat flour contains the special proteins glutenin and gliadin which when mixed together form gluten. Gluten is a large network, which is very viscous and elastic. It is this network, which gives the doughs their unique consistency and holds the gas from yeast fermentation during baking to form the open crumb structure of the finished leavened bread. Other cereals such as barley, rye and soya do not have this type of gluten and so form heavier, denser breads. Modification of this gluten protein with exogenous proteases can have a dramatic effect on the appearance of the bread. Proteases are also used to weaken gluten to give more plastic dough properties required for making biscuits.

Chemical oxidants such as bromates (potassium bromate) and ascorbic acid are also used in baking to strengthen the gluten. Enzymes such as glucose oxidase can replace such chemical oxidants. This enzyme oxidises sulphydryl groups in the gluten chemical structure to make the dough stronger and more elastic.

The non-starch polysaccharides in flour also play an important role in bread quality as they are responsible for much of the water absorption in dough and interact with the gluten complex. The addition of xylanases and other fibre-degrading enzymes have been shown to have a dramatic effect on the dough and finished bread characteristics.

Recently lipases have become available for use in bread making. Certain types of lipids have an influence on staling and the organoleptic properties of bread. Some of the lipases already commercialised for other purposes are being used in bread making. It is expected that a new generation of lipases specific to bread making will be available soon.

The interactions between enzymes on the various components of bread dough is a very complex subject and the wrong enzyme cocktail or even the wrong application rate can result in detrimental effects on either the dough or the finished bread. For example too much enzyme usually results in a loss of structure, resulting in bread that does not rise properly or that will cause problems in bakery machinery because it is too sticky.

Detergents

Enzymes have been used in the detergent industry since the mid 1960’s and are 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 "cocktail" of enzyme activities including lipases and amylases. Lipases are effective on stains resulting from fatty products such as oils and fats 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.

Pharmaceuticals and Diagnostics

Enzymes have many roles in the pharmaceutical and diagnostic industries. There are too many applications to cover but typical applications include:

• Enzymes as direct pharmaceutical products such as in the treatment of genetic disorders leading to a specific enzyme deficiency.
• Extraction of medicinally important compounds such as heparin.
• Manufacture of chemical pharmaceuticals where enzymes are used for the interconversion of chemical intermediates.
• Combinatorial bio catalysis.
• Research and development - especially in the field of molecular biology where almost all the processes of nucleic acid manipulation are performed with enzymes (eg. restriction endonucleases and DNA polymerases).
• Diagnostic procedures also frequently utilise enzymes - one example include glucose oxidase.

Enzymology

Enzymology is a critical part of understanding the cause of diseases. Most genetic diseases are a result of a particular enzyme deficiency. Similarly certain bacteria are more pathogenic because of an enzyme activity they possess. 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) - try looking for websites describing ELISA. 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: 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 (myocardial infarction, embolisms and deep venous thrombosis) is called tissue plasminogen activator. Nuclease is considered as a possible therapy for cystic fibrosis, but it is not clear how commercialised and therapeutically successful this has been.
• Proteases are also used in wound therapy. In this case they are called debriding agents and are used to clean a wound and therefore accelerate 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.  

Some of my information has come from:

• “A New Introduction to Biology” by Bill Indge, Martin Rowland and Margaret Baker
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• “AS Biology Revision” by Letts