A CRITICAL STUDY ON ENZYMES. A RESEARCH PROJECT MATERIAL ON BIOCHEMISTRY
CHAPTER ONE
INTRODUCTION AND LITERATURE REVIEW
1.1 Enzyme
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).
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