What are enzymes and why do we use them in laundry detergents?

What are enzymes?

They're proteins produced by all living organisms that act as catalysts to speed up chemical reactions that would otherwise occur at a much slower rate or not at all. Would the reader understand catalyst? Perhaps a simple explanation "Catalysts are materials that help reactions move from a beginning to an end. Catalysts are not used up in the reaction so they are available to help multiple reactions."

Enzymes fit their target substrates like a lock fits a key.

The active site of the enzyme is open only to specific target substances (i.e., substrates) with a matching chemical and 3-dimensional shape. If the substrate doesn't fit, it can't enter and no reaction occurs. This makes the action of enzymes highly specific for their substrates.

A little enzyme goes a long way!

Like other types of catalysts, an enzyme can complete its chemical reaction without being used up or destroyed, leaving the enzyme protein available for yet another reaction. This means that one enzyme protein molecule can act on many substrate molecules. Eventually, all the substrate is gone and the enzyme stops working.
Also, the enzyme will eventually break down on its own.

Why is this important in a laundry detergent?

The enzymes used in laundry detergents act on materials that make up a variety of stains and soils so that these materials can be washed away more easily. These enzymes are named after the materials they can act upon, for example, proteases break down protein based stains, lipolases break down lipid (fat) based stains and amylases break down starches and other carbohydrate based stains (amyl is Greek for starch). Since one enzyme molecule can act on many substrate (i.e., soil) molecules, a small amount of enzyme added to a laundry detergent can provide a big cleaning benefit to the consumer.

Are enzymes safe?

Enzymes are proteins, therefore, they are completely biodegradable. They are non-toxic to plants and animals in the environment. They are harmless if accidentally ingested by a child. However, like many other proteins, enzymes can cause respiratory allergy in some people if they are breathed in at very high concentrations, frequently, and for long periods of time. This doesn't pose a safety issue for consumers who use laundry detergents. However, this can represent a health issue for people that work in enzyme making facilities and in detergent production facilities, especially if enzymes are not handled properly.

What's a respiratory allergy?

Respiratory allergy is a response our bodies can have when we are exposed to proteins such as house dust mites, cat and dog dander, pollens, molds. Not everyone will develop respiratory allergy to the variety of proteins we are exposed to on a daily basis. As mentioned above, enzymes are proteins. Frequent inhalation of enzymes at high concentrations over a long period of time can lead to respiratory allergy among some people. This can occur among people that have to work with enzymes and when the enzymes are not handled properly.

Enzymes in the workplace.

When enzymes were first introduced into detergent products in the 1960s, they were dusty powders. The detergent products were also very dusty so it was easy for the enzymes to become airborne. At that time there were very few controls to limit the amount of detergent powder that could become airborne during the making and packing of detergents. As a result, many employees were exposed to very high levels of airborne enzyme and some of them developed respiratory allergies. Since then, a number of steps have been taken to eliminate the health risk to our employees by reducing the amount of airborne enzyme in the workplace. Some of these steps are:

Receiving and handling enzymes in completely enclosed systems to further limit exposure
Improved engineering and ventilation to minimize generation of dust
Constant monitoring of airborne enzyme levels in the manufacturing plants to allow early identification of leaks or other problems so that they can be addressed promptly.
Development of standard practices to clean up spills and perform other tasks in a manner that limits the potential to generate airborne dust.
A thorough health monitoring program for each employee to limit the chances of development of respiratory allergy.

References:

The following are selected enzyme references:

Flindt, M. L. H. 1969. Pulmonary disease due to inhalation of derivatives of Bacillus subtilis containing proteolytic enzyme. Lancet, 1:1177-81.
Pepys J., J. L., Longbottom, F. E. Hargreave and J. Faux. 1969. Allergic reactions of the lungs to enzymes from Bacillus subtilis. Lancet, 1:1181-4.
Newhouse M. L., B. Tagg, S. J. Pocock, A. C. McEwan. 1970. An epidemiological study of workers producing enzyme washing powders. Lancet, 1:689-693.
Juniper, C. P., M. J. How, B. F. J. Goodwin and A. K. Kinshott. 1977. Bacillus subtilis enzymes: a 7-year clinical, epidemiological and immunological study of an industrial allergen. J. Soc. Occup. Med., 27:3-12.
Flood D. F. S., R. E. Blofeld, C. F. Bruce, J. I. Hewitt, C. P. Juniper and D. M. Roberts. 1985. Lung function, atopy, specific hypersensitivity, and smoking of workers in the enzyme detergent industry over 11 years. Br J Ind Med.,42:43-50.
Schweigert, MK, MacKenzie, DP and Sarlo, K. 2000. Occupational asthma and allergy associated with the use of enzymes in the detergent industry - a review of the epidemiology, toxicology and methods of prevention. Clinical and Experimental Allergy, 30: 1511-1518.
Sarlo, K and Kirchner, DB. 2002. Occupational asthma and allergy in the detergent industry: new developments. Current Opinion in Allergy and Clinical Immunology, 2:97-101.
Sarlo, K. 2003. Control of occupational asthma and allergy in the detergent industry. Annals Allergy, Asthma and Immunology, 90(suppl):32-34.

In addition, a complete literature review on enzymes was recently completed by the European Union:

Aberer, W., M. Hahn, M. Klade, U. Seebacher, A. Spök, K. Wallner and H. Witzani. 2002. Final report: Collection of information on enzymes, European Commission Contract No. B4-3040/2000/27845/MAR/E2

http://europa.eu.int/comm/environment/.../enzymerepcomplete.pdf