UNIT 7 ENZYMOLOGY

Learning Objectives Explain the role of enzymes as biological catalyst State the general properties of enzymes Classify enzymes Explain enzyme specificity Explain mechanism of enzyme action State the factors that affect the rate of enzyme catalyzed Describe and classify coenzymes List the diagnostic value of plasma enzymes

Learning Objectives Explain the role of enzymes as biological catalyst State the general properties of enzymes Classify enzymes Explain enzyme specificity Explain mechanism of enzyme action State the factors that affect the rate of enzyme catalyzed Describe and classify coenzymes List the diagnostic value of plasma enzymes

The Role of Enzymes Biological catalysts brings chemical reaction Produced by living organisms Present in very small amounts in cells Functions in the body: (catalyzed & controlled by enzymes) Digestion Breathing Synthesis and breakdown of CHO, COOH & CHON

Substrate a substance on which the enzymes acted on it converted to product/s. -ase (how the enzymes are named) “Acts” E.g. Lactase - enzyme Lactose - substrate forming the products (glucose + galactose)

All enzymes are proteins it follows the physical and chemical reaction of proteins. They are heat labile Soluble in water Precipitated by protein precipitating reagents (e.g. ammonium sulphate or trichloroacetic acid) Contain 16% weight nitrogen

Learning Objectives State the general properties of enzymes Explain the role of enzymes as biological catalyst State the general properties of enzymes Classify enzymes Explain enzyme specificity Explain mechanism of enzyme action State the factors that affect the rate of enzyme catalyzed Describe and classify coenzymes List the diagnostic value of plasma enzymes

General Properties of Enzymes All enzymes are proteins They accelerate the reaction, but Do not alter the reaction equilibrium Not consumed in overall reaction Required only in very small quantities They have enormous power for catalysis

Enzymes are highly specific for their substrate Enzymes posses active sites at which interaction with substrate takes place Enzymes lower activation energy They form substrate complex as intermediates during their action Some enzymes are regulatory in function

Learning Objectives Classify enzymes Explain the role of enzymes as biological catalyst State the general properties of enzymes Classify enzymes Explain enzyme specificity Explain mechanism of enzyme action State the factors that affect the rate of enzyme catalyzed Describe and classify coenzymes List the diagnostic value of plasma enzymes

CLASSIFICATION OF ENZYMES 1. OXIDOREDUCTASES (one compound oxidized, another is reduced) 3. HYDROLASES (hydrolysis of esters, ether, peptide / glycosidic bond) > Enzyme helps in hydrolysis of chemical bonds by addition of water molecules 2. TRANSFERASE (transfer group containing C,N,or S from one substrate to another substrate)

CLASSIFICATION OF ENZYMES OXIDOREDUCTASES e.g. tyrosinase,urease, catalase, peroxidase HYDROLASES e.g. esterases, peptidases TRANSFERASE e.g. transaminases, hexokinases Lactate dehydrogenase Pyruvate Lactate NAD NADH+H+ Serine dehydrogenase Serine Glycine Methyl transferase Urease “Split” Urea + H2O CO2 + 2NH3

CLASSIFICATION OF ENZYMES 4. LYASES (catalyze the addition or removal of groups without hydrolysis, oxidation or reduction producing double bonds) 6. LIGASES (also called as synthesases link two substrates together by pyrophosphate bound in ATP) 5. ISOMERASES (produce geometric or position isomers of substrates by intermolecular rearrangement)

CLASSIFICATION OF ENZYMES LYASES e.g. decarboxylases, carboxylases, carbonic anhydrase LIGASES e.g. glutamine synthetase ISOMERASES e.g. reacemases, epimerases, isomerases Pyruvate Pyruvate Acetaldehyde + CO2 Dehydrogenase Mutase Succinyl CoA Methyl Malonyl CoA Pyruvate Carboxylase Pyruvate Oxaloacetate ATP ADP + Pi

Explain enzyme specificity Learning Objectives Explain the role of enzymes as biological catalyst State the general properties of enzymes Classify enzymes Explain enzyme specificity Explain mechanism of enzyme action State the factors that affect the rate of enzyme catalyzed Describe and classify coenzymes List the diagnostic value of plasma enzymes

SUBSTRATE SPECIFICITY ENZYME SPECIFICITY STEREOSPECIFICITY SUBSTRATE SPECIFICITY REACTION SPECIFICITY

ENZYME SPECIFICITY SUBSTRATE SPECIFICITY REACTION SPECIFICITY STEREOSPECIFICITY ENZYMES SHOW SPECIFICITIES ONLY WITH A SPECIFIC GROUP OF A SUBSTRATE (e.g. urease catalyses the hydrolysis of urea) ENZYMES CATALYZE SIMILAR TYPE OF REACTION BUT DIFFER IN THEIR ACTION DUE TO SUBSTRATE SPECIFICITY Example: Pepsin hydrolysis – peptide bond (phenyl alanine & tyrosine) b. Trypsin (peptide bond – arginine or lysin) SUBSTRATE SPECIFICITY A SUBSTRATE CAN UNDERGO MANY REACTIONS BUT IN REACTION SPECIFICITY, ONE ENZYME – CATALYZE ONE REACTION (Example: OXALIC ACID – catalyze by separate enzymes) REACTION SPECIFICITY

SUBSTRATE SPECIFICITY ENZYME SPECIFICITY STEREOSPECIFICITY REACTION SPECIFICITY SUBSTRATE SPECIFICITY

Explain mechanism of enzyme action Learning Objectives Explain the role of enzymes as biological catalyst State the general properties of enzymes Classify enzymes Explain enzyme specificity Explain mechanism of enzyme action State the factors that affect the rate of enzyme catalyzed Describe and classify coenzymes List the diagnostic value of plasma enzymes

MECHANISM OF ENZYME ACTION Combines w/ substrate P E E : Enzyme molecule P : Product S : Substrate molecule E : Enzyme ES : Enzyme-Substrate

MECHANISM OF ENZYME ACTION P E Active Site/Catalytic Site : The site at which a substrate can meet with enzyme. It is made up of several amino acid.

Learning Objectives Explain the role of enzymes as biological catalyst State the general properties of enzymes Classify enzymes Explain enzyme specificity Explain mechanism of enzyme action State the factors that affect the rate of enzyme catalyzed Describe and classify coenzymes List the diagnostic value of plasma enzymes

FACTORS AFFECTING ENZYME ACTIVITY SUBSTRATE CONCENTRATION Low substrate concentration, the enzyme is not saturated 2. ENZYME CONCENTRATION The rate of enzyme catalyzed reaction is directly proportional to the concentration of the enzyme.

FACTORS AFFECTING ENZYME ACTIVITY 3. EFFECT OF pH Excessive changes in pH  completely denature and inactive enzymes Optimum pH: enzyme activity is maximum at a particular pH.

FACTORS AFFECTING ENZYME ACTIVITY 4. EFFECT OF TEMPERATURE: The velocity of enzyme reaction increases when temperature of the medium is increased  denatured by heat & becomes inactive. Optimum temperature: the temperature at which maximum amount of substrate is converted to the product per unit time

FACTORS AFFECTING ENZYME ACTIVITY 5. EFFECT OF TIME : The time required for completion of an enzyme reaction increases with decrease in temperature from its optimum. 6. ENZYME INHIBITION Inhibitors – chemical substances which inactivate the enzymes. Inhibitors, e.g. Poisons (harmful)

Describe and classify coenzymes Learning Objectives Explain the role of enzymes as biological catalyst State the general properties of enzymes Classify enzymes Explain enzyme specificity Explain mechanism of enzyme action State the factors that affect the rate of enzyme catalyzed Describe and classify coenzymes List the diagnostic value of plasma enzymes

CO-ENZYMES Loosely bound Removed by dialysis Low molecular weight Non-protein organic compound Heat resistant Function as co substances Loosely bound Removed by dialysis Tightly bound – prosthetic group of enzyme Water soluble vitamins: Vit. B complex & Vit. C (co-enzymes)

refers to the protein part of enzyme CO-ENZYMES CONJUGATED PROTEIN ENZYME = PROTEIN + PROSTHETIC GROUP HOLOENZYME = APO-ENZYME + CO-ENZYME PROTEIN PART + NON-PROTEIN PART (PROSTHETIC GROUP) APO-ENZYME: refers to the protein part of enzyme

CLASSIFICATION OF CO-ENZYMES CO-ENZYMES FOR GROUP TRANSFER OF GROUPS OTHER THAN H CO-ENZYMES FOR TRANSFER OF H ATP and its relatives CoA B6 phosphate Cobalamine (B12) co-enzyme Biotin Lipoic acid Thiamine Sugar phosphates Folate co-enzymes NAD, NADP FAD LIPOIC ACID CO-ENZYME Q

Learning Objectives List the diagnostic value of plasma enzymes Explain the role of enzymes as biological catalyst State the general properties of enzymes Classify enzymes Explain enzyme specificity Explain mechanism of enzyme action State the factors that affect the rate of enzyme catalyzed Describe and classify coenzymes List the diagnostic value of plasma enzymes

Sr. ENZYMES INCREASED IN 1 AMYLASE Acute Pancreatitis 2 ACID PHOSPHATASE (pH=5) Prostatic carcinoma 3 ALKALINE PHOSPHATASE (pH=10) Liver disease, rickets 4 ASPARTATE TRANSAMINASE (AST) Myocardial Infarction 5 ALANINE TRANSAMINASE (ALT) Liver disease (liver cell damage) 6 LACTATE DEHYDROGENASE (LDH) 7 CREATINE KINASE (CK) Myocardial Infarction and Skeletal Muscle disease 8 GLUTAMYL TRANSFERASE Liver disease, biliary obstruction and alcoholism

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