ENZYMES

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ENZYMES PREPARED BY: M.SAKTHIVEL (BSA-09-841)

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CONTENTS: Enzymes History of enzymes Occurence and distribution Enzyme nomenclature Terminologies used Theories of enzyme binding Classification of enzymes Factors affecting enzymes rate

ENZYMES: 

ENZYMES An enzyme is a protein that is synthesized in a living cell and catalyses or speed up a thermodynamically possible chemical reaction The enzyme in no way modifies the equilibrium constant (K eq ) or the free energy change (ΔG) of a reaction.

How do enzymes work & why are they needed? : 

How do enzymes work & why are they needed? Enzymes work by breaking apart large, complex compounds (substrates) into smaller, more readily absorbed nutrients that the bacteria can absorb. Each enzyme is designed to unlock and break down a specific food source.

HISTORY OF ENZYMES: 

HISTORY OF ENZYMES The enzyme (in yeast) was proposed by Kuhne in 1877 to distinguish enzyme from organized and unorganized ferments. In 1836, J.J Berzelius named the biological agent as ‘diastase’ which is known today as amylase capable of converting starch from malt extract into sugar. Pasteur working on microorganism concluded that fermentation and similar processes could be performed only by living cells

STRUCTURE OF ENZYMES: 

STRUCTURE OF ENZYMES T hey have a globular shape A complex 3-D structure ex.Human pancreatic amylase

OCCURRENCE AND DISTRIBUTION: : 

OCCURRENCE AND DISTRIBUTION: Enzymes occur in all living cells but not all enzymes are found in all the cells . The enzymes catalyse a wide variety of biochemical reactions many of which are localized in specific organs or are peculiar to certain species of plant or animal life .

Contd….: 

Contd …. A few of the enzymes are present in most forms of life .ex- ample,catalases and peroxidases are widely distributed in all higher plants and animals. The amount of enzymes may be different in different tissues.For example, resting seeds have low activity of amylases and proteinases while the germinated seedlings have more activity.

Enzyme Nomenclature  : 

Enzyme Nomenclature The different kinds of enzymes are named in different ways. Most often enzymes are named by adding a suffix ' ase ' to the root word of the substrate. For example, Lipase (fat hydrolysing enzyme), Sucrase (breaking down sucrose). Sometimes the enzymes are named on the basis of the reaction that they catalyse . For example, Polymerase (aids in polymerisation ), Dehydrogenase (removal of H atoms).

Contd..: 

Contd.. Some enzymes have been named based on the source from which they were first identified. For example, Papayin from papaya. The names of some enzymes ends with an 'in' indicating that they are basically proteins.For example, Pepsin, Trypsin etc

Microbial Enzymes: 

Microbial Enzymes Used in applications from food production to molecular biology research Microbial enzymes are active in a pH range of 3.0 - 9.0, whereas animal enzymes require a pH over 5.0 to work effectively Some of the first commercially available enzymes were DNA polymerases and restriction enzymes

TERMINOLOGIES : 

TERMINOLOGIES Some of the terms used in enzymology are defined below: SUBSTRATE : The substance acted upon by the enzyme. PRODUCT : The substance formed as a result of the enzymatic action. ACTIVE SITE : The site other than the active site on the enzyme wherein the effector or modulator is bound and controls the rate of enzyme-catalyzed reaction. REGULATORY SITE: The site other than the active site on the enzyme wherein the effector or modulator is bound and controls the rate of enzyme – catalysed reaction. HOLOENZYME: A completely catalytically active enzyme.

THEORIES FOR ENZYME- SUBSTRATE BINDING: 

THEORIES FOR ENZYME- SUBSTRATE BINDING Two theories have been proposed to explain interaction of substrate and enzyme. LOCK AND KEY MODEL INDUCED-FIT THEORY

LOCK AND KEY MODEL : 

LOCK AND KEY MODEL According to the lock and key model proposed by Emil Fisher in 1894,the substrate and enzyme have structural complementarity and fit together like lock and key i.e ,, the active site of the enzyme has a complementary shape of the substrate to form an enzyme-substrate complex . This model has proved to be essentially correct in the case of enzymes known to exhibit absolute specificity.

LOCK AND KEY MODEL : 

LOCK AND KEY MODEL

INDUCED-FIT THEORY : 

INDUCED-FIT THEORY This theory proposed by D.E . Koshland in1968 suggests that the substrate binds at the active site of the enzyme and then modifies the shape of the active site so that it becomes complementary for the substrate binding . For example, binding of substrate to lysozyme takes place in this way.

INDUCED-FIT THEORY : 

INDUCED-FIT THEORY

Classification of Enzymes : 

Classification of Enzymes Enzymes are generally classified on the basis of the type of reactions that they catalyse . 6 groups of enzymes can be recognised on this basis. The following table lists the 6 groups of enzymes along with example.

FACTORS AFFECTING THE RATE OF ENZYME-CATALYZED REACTIONS : 

FACTORS AFFECTING THE RATE OF ENZYME-CATALYZED REACTIONS Several factors are known to influence the rate of enzyme-catalyzed reaction ,chief of them being: 1.Enzyme concentration 2.Substrate concentration 3.Temperature 4.pH and 5.Activators and inhibitors.

SOME OF THE ENZYMES: 

SOME OF THE ENZYMES Amylase: An enzyme which degrades starch and similar carbohydrates e.g. rice, potatoes etc. Cellulase : An enzyme which degrades cellulose and is effective on digesting paper Lipase: An enzyme which degrades fats, oils and greases (FOG's) Protease: An enzyme which degrades proteins e.g. food residue. Uricase : An enzyme which degrades Uric Acid

REFERENCE: 

REFERENCE The textbook of AGRICULTURAL MICROBIOLOGY published by S.K.Thimmaiah Ist edition in 1999. Chapter:6 Page no: 152-192. http:// www.biosmarttechnologies.com/bacteria-enzymes.html

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