A CRITICAL STUDY ON ENZYMES
INTRODUCTION AND LITERATURE REVIEW
Enzymes are large biological molecules responsible for thousands of chemical inter-conversions that sustain life (Smith, 1997). All known enzymes are proteins. They are high molecular weight compounds made up principally of chains of amino acids linked together by peptide bonds, they are denatured at high temperature and precipitated with salts, solvents and other reagents. They have molecular weights ranging from 10,000 to 2,000,000 units. Enzymes do not cause reactions to take place, but rather they enhance the rate of reactions that would have been slower without their presence and still remains unused and unchanged.
Many enzymes require the presence of other compounds - cofactors - before their catalytic activity can be exerted. This entire active complex is referred to as the holoenzyme; i.e. apoenzyme (protein portion) plus the cofactor (coenzyme, prosthetic group or metal-ionactivator) is called the holoenzyme (Alexopoulos et al., 1996)
The living cell is the site of tremendous biochemical activity called metabolism. It is the process of chemical and physical change which goes on continually in the living organism involving the build-up of new tissues, replacement of old tissue, conversion of food to energy, disposal of waste materials, reproduction - all the activities that we characterize as "life."Thephenomenon of enzyme catalysis makes possible biochemical reactions necessary for all life processes. Catalysis is defined as the acceleration of a chemical reaction by some substance which itself undergoes no permanent chemical change. Synthetic molecules called artificial enzymes also display enzyme like catalysis (Grovesm, 1997).
The catalysts of biochemical reactions are enzymes and are responsible for bringing about almost all of the chemical reactions in living organisms. Without enzymes, these reactions take place at a rate far too slow for the pace of metabolism(Bairoch, 2000).
Enzymes actually work by lowering the activation energy of a reaction. This is achieved when it creates an alternative pathway which is faster for the reaction hence speeding it up such that products are formed faster. Enzyme catalysed reactions are million times faster than uncatalysed reactions, they alter the rates but not the equilibrium constant of the reaction being catalysed (Ashokkumar et al., 2001). A few RNA molecules called ribozymes also catalyse reactions, with an important example being some parts of ribosome (Lilley, 2005).
1.1.1 Types of enzymes
Metabolic enzymes: These have been called the spark of life, the energy of life and the vitality of life. These descriptions are not without merit. Metabolic enzymes catalyse and regulate every biochemical reaction that occurs within the human body, making them essential to cellular function and health (Sangeethaet al.,2005). Digestive enzymes turn the food we eat into energy and unlock this energy for use in the body. Our bodies naturally produce both digestive and metabolic enzymes as they are needed. They either speed up or slow down the chemical reactions within the cells for detoxification and energy production. The enable us to see, hear, and move and think. Every organ, every tissue and all 100 trillion cells in our body depend upon the reaction of metabolicenzymes and enjoy their energy factor. Without these metabolic enzymes, cellular life would beimpossible.
Food enzymes:These are introduced to the body through the raw foods we eat and throughconsumption of supplemental enzyme products. Raw foods naturally contain enzymes providing asource of digestive enzymes when ingested(Hossainet al., 1984). However, raw food manifests only enough enzymesto digest that particular food, not enough to be stored in the body for later use (the exceptionsbeing pineapple and papaya, the sources of the enzymes bromelain and papain). The cooking andprocessing of food destroys all of its enzymes. Since most of the foods we eat are cooked orprocessed in some way and since the raw foods we do eat contain only enough enzymes toprocess that particular food (Persike et al., 2002) our bodies must produce the majority of the digestive enzymes werequire, unless we use supplemental enzymes to aid in the digestive process. A variety ofsupplemental enzymes are available through different sources. It is important to understand thedifferences between the enzyme types and ensure that one is using an enzyme product which willmeet one’s particular needs.
Plant based enzymes:These are the most popular choice of enzymes. They are grown in a laboratorysetting and extracted from Aspergillus species. The enzymes harvested from Aspergillusspecies are called plantbased, microbial and fungal. Of all the choices, plant based enzymes are the most active. Thismeans they can break down more fat, protein and carbohydrates in the broadest pH range than any other sources (Ashokkumar et al., 2001).
1.1.2 Characteristics of enzymes
Protein nature:Enzyme is a protein. The main components of an enzyme is protein.
Temperature:Enzymes are sensitive to temperature. Many work best at temperatures close to body temperatures and most lose their ability to catalyse if they are heated above 60 or 70o C. (Ashokkumar et al., 2001).
Acidity and alkalinity:Many enzymes work best at a particular pH and stop working if the pH becomes too acidic or alkaline.
Catalytic effect:It acts as catalyst, enzyme functions in accelerating chemical reaction, but the enzyme itself does not change after the reaction ends.
Specificity:It functions specifically. The enzyme only catalyzes one kind of substrate and cannot function for many substrates. The term is called one enzyme one substrate.
Reversibility: It means the enzyme does not determine the direction of reaction, but it only functions in accelerating reaction rate until it reaches equilibrium. The enzyme also functions in substance synthesis and substance breaking down reaction.
Small quantity:It is required, in small amount. A small amount of enzyme is able to catalyze a chemical reaction (Nason, 1968).