Enzymes are present in every cell of every living entity, from simple single cellular organisms to highly complex multi-cellular organisms, including human beings. Enzymes are a critical element of our daily lives. They perform functions ranging from assisting in producing the food we eat to providing therapeutic agents contributing to the care of our health. Enzymes can perform all of these functions because they are:
Proteins: Enzymes, like other proteins, consist of long chains of amino acids held together by peptide bonds. Enzymes perform the vital function of controlling the metabolic processes in which nutrients are converted into energy and fresh cell material. For example, in the digestive tract, enzymes like pepsin, trypsin, lipase, and amylase break down food compounds into simpler compounds that are then converted into energy for the body.
Bio-Catalysts: Enzymes are substances that accelerate chemical reactions without being consumed in the process. Industrial enzymes are most frequently applied to biochemical reactions in which high molecular weight substances, like starches, proteins, celluloses, etc., require hydrolytic decomposition. In nature, enzymes control the build-up and decomposition of essential matter in vegetable and animal organisms.
Specific: Each enzyme catalyzes a specific chemical reaction. Essentially, each enzyme breaks down or synthesizes one particular compound, or can even be limited to specific bonds in the compound they react in. For example, pectinase can only degrade pectin, not starch or cellulose.
Efficient: Enzymes are efficient catalysts. For instance, one catalase enzyme molecule can catalyze the breakdown of five million molecules of hydrogen peroxide into water and oxygen in just one minute. The enzyme catalase is found in the liver and red blood cells in large quantities.
Sources and Types of Enzymes
The three major sources of enzymes are:
♦ Plant Enzymes: These enzymes are derived from a variety of plants and are effective within a broad pH range. Papain, bromelain, ficin have predominantly proteolytic activity, but amylolytic enzymes of cereals, soybean lipoxygenase, and specialized enzymes from citrus fruits also fall in this category.
♦ Animal Enzymes: Derived from animal glands, this category includes the pancreatic enzymes, trypsin, lipase, rennet, and other enzymes like pepsin. These enzymes are actively limited to a very narrow pH range, are very specific in action, and may have a delayed effect.
♦ Microbial Enzymes: These fungal and bacterial enzymes are derived from microorganisms through a process of fermentation. Enzymes amylases, diastases, etc., begin working immediately under broad pH range.
Approximately eighty percent of all industrial enzymes are hydrolic in nature and used for depolymerization of natural substances. (Depolymerization is the breaking down of complex molecules into simpler molecules.) Of these enzymes, sixty percent are proteolytic enzymes used by the detergent, dairy and leather industries. Thirty percent are carbohydrases used in the baking, distilling, brewing, starch, and textile industries. This leaves lipases and highly specialized enzymes for use in pharmaceutical, analytical, and developmental industries.
Enzyme Selection Factors
Generally, the following factors are considered when selecting an enzyme for a particular process:
♦ Specificity: It is of prime importance to understand that enzymes are very specific in their action, which depends upon the source and type of enzyme. One enzyme can act on many molecules but on only one specific substrate to give one particular result. This can be an advantage used to obtain precise reaction products.
♦ pH: Each enzyme type has an optimal pH range in which it is most effective. A bbroader pH range provides a greater margin to operate within. A narrow pH range is useful when a very specific action is required.
♦ Temperature: In enzyme processes, the general rule is that the temperature quotient is between 1.8 and 2.0. The reaction rate generally increases or decreases by this order for each shift of 10°C. By using high temperatures, the reaction may be of short duration and hygienic conditions may be maintained more easily. The enzyme's performance increases with a rise in temperature until heat inactivation takes place.