ENZYMOLOGY

INTRODUCTIONDr.Geeta Jaiswal

All the reactions in the body are mediated by specialized .proteins which act as biocatalysts and are called enzymes.

They function in the acceleration of chemical reactions

Clinical enzymology is an important branch of medicine.

It basically deals with the use of enzymes for diagnosis, prognosis and therapy ( treatment of disease)

In hospital labs, enzyme assays may account for 40 to 50 percent of the work load with as many as 20 to 30 enzymes being estimated routinely

DEFINITIONEnzymes are catalysts of biological systems.

They are important biomolecules synthesized by the living system

They are colloidal thermo labile and protein in nature

They are remarkable molecular devices which determine the pattern of chemical transformations in biological systems.

They also mediate transformations of different forms of energy

SHARED PROPERTIES WITH CHEMICAL CATALYST

Enzymes are neither consumed nor produced during the course of reaction

They do not cause reactions to take place They just enhance the rate of reaction

that would proceed much slower in their absence

They alter the rate but not the equilibrium constant of the reaction.

Protein Nature of Enzymes

All enzymes are proteins in nature with large molecular weight

Ribozymes however are an exception , being RNA molecules with enzymatic activity

Few enzymes are simple proteins while some are conjugate proteins

Enzymes which are conjugated proteins have a non-protein part called the prosthetic group or Co-enzyme.

Holoenzyme = Apoenzyme (protein part) + Co-enzyme (Prosthetic Group)

Monomeric enzymes & OligomericEnzymes: Monomeric Enzymes:- When the enzyme

protein is made up of one polypeptide chain.

Oligomeric Enzymes: - When an enzyme molecule is made up of more than one polypeptide chain it is called oligomeric. Each polypeptide chain of such enzymes are called subunits or monomer units eg: Hexokinase, LDH.

Multienzyme Complex

When different enzyme catalyzing sites are located in the same macromolecule it is called a multienzyme complex.

Eg: Fatty acid synthetase system, Pyruvate dehydrogenase System, Prostaglandin Synthase System.

6 Other Characteristics ofEnzymes.(Differentiating them from chemical Catalysts)

Substrate : Substances on which the enzyme acts to convert them to products are called SUSTRATES.

Hexokinase Glucose Glucose 6 P ATP ADP

Enzyme Substrate Complex

Enzymes may show high specificity towards one substrate, or exhibit broad specificity using more than one substrate.

Enzymes usually function within a moderate pH and temperature range.

Active Site Active Site: Enzyme molecules

contain special pockets or clefts called active sites.

The active site contain amino acid side chains which create a three dimensional surface complementary to substrate.

Location within the Cell Many enzymes are localized in specific

organelles within the cell Such compartmentalization serves to

isolate the reaction substrate or productIt also provides a favorable environment

for the reactionIt organizes thousands of enzymes

present inside the cell into purposeful pathways for example :

Location of Enzymes inside CellCYTOSOL MITOCHONDRIA NUCLEUS LYSOSOMES

Glycolysis T.C.ACycle

RNASynthesis

Degradation of complex molecules

H.M.PShunt

F.A.oxidationB-oxidation

DNASynthesis

F.A.Synthesis

PyruvateDecarboxylation

The active site binds the substrate forming an Enzyme –Substrate complex (ES).

ES is converted to Enzyme –Product (EP), which subsequently dissociates to enzyme and product.

Enzyme –Substrate complex

ES Complex and product formation

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