enzyme by cvas,bikaner boys

8/9/2019 Enzyme by cvas,bikaner boys

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Enzymes

Pepsi

n

BY

Tarachand nayak &

Umesh kr prajapatCVAS,Bikaner


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What are enzymes?

Enzymes are proteins (globular). Act as organic enzymes.

Enzymes speed up the rate of a chemical

reaction without themselves being used up(consumed) during the reaction.

Are essential to the functioning of all cells.Without enzymes, metabolism would be too slow

& insufficient energy would be available tomaintain life.


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Enzymes are the proteinsthat provide function to thecell.

Enzymes are catalysts:they speed up chemical

reactions.Image


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Name of Enzymes

End in ase Identifies a reacting substance

sucrase reacts sucroselipase - reacts lipid Describes function of enzyme

oxidase catalyzes oxidation

hydrolase catalyzes hydrolysis Common names of digestion enzymes stilluse in

pepsin, trypsin


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Classification of Enzymes

Class Reactions catalyzed

Oxidoreductoases oxidation-reduction

Transferases transfer group of atoms Hydrolases hydrolysis

Lyases add/remove atomsto/from a double bond

Isomerases rearrange atoms Ligases combine molecules

using ATP


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Examples of

Classification of Enzymes Oxidoreductoases

oxidases - oxidize ,reductases reduce Transferases

transaminases transfer amino groupskinases transfer phosphate groups

Hydrolasesproteases - hydrolyze peptide bonds

lipases hydrolyze lipid ester bonds Lyases

carboxylases add CO2

hydrolases add H2O


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CHEMICAL NATURE OFENZYMES

HOLOENZYME=APOENZYMES+COENZYMES(active en.) (protein part) (non protein)

WORKING

OF ENZYMES


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SPECIFICTY OF ENZYMES


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Factors affecting enzyme

activity.Enzymes are very sensitive to conditions inwhich they work. They usually have a narrowrange of conditions under which they operateproperly.

Factors affecting enzyme activityTemperature.pH.Enzyme concentration.Substrate concentration.Enzyme inhibitors


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activity.TemperatureEnzymes usually work best in the temperature of

the environment in which they are found in.

e.g. most human enzymes have an optimumtemperature of ~37C (= body temperature).

At high temp enzymes are permanentlydenatured.

At low temp enzyme activity slows down,however no permanent damage is done to theenzyme.


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activity.Temperature


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activitypHMost human enzymes have an optimum pH

between 6 and 8. e.g. Trypsin has an optimum pHof 8.0.

Enzymes that are secreted into the stomach havea much lower optimum pH. e.g. Pepsin has anoptimum pH of 1.5.

If pH is too high or low, enzyme can becomedenatured.


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activitypH


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activity.Enzyme concentration Rate of reaction

continues to increase

with an increase inenzymeconcentration(assuming non

limiting amount ofsubstrate)


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activity.Substrate concentration Rate of reaction

increases up to a

point. After this ratelevels off because allenzyme moleculesare working at their

maximum capacity(i.e. active sites aresaturated).


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activity.Enzyme inhibitors Two typesCompetitive inhibitors block the active site and

stop the substrate from getting in there.e.g. poisons such as arsenic

Non-competitive inhibitors bind to enzyme (butnot the active site) and cause it to change shape.


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actionSubstrate concentrationMax. Rate

R

ateo

freaction

Substrate

conc.


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MICHEALIS MENTON EQUATION

Vi = V max [S]Km + {S}

Vi = Measured initial velocityV max = Maximum velocityS = SubstrateKm = Michaelis constantVariationsA. When (S) is much less than KmVi = V max [S] OR V max [S] K [S]

Km + {S} KmSo Vi depends upon substrate concentration


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ENZYME INHIBITION

Competitive inhibition Non competitive inhibition Irreversible inhibition

Competitive inhibition Inhibitors resemble substrate, Km is increased no

change in Vmax Succinate Enz Fumarate Malonate (structural analog of Succinate ) Enz

inhibitionno product Drug Allopurinol, structural analog of Xanthene is used

for treatment of gout /hyperuricemia as it is acompetitive inhibitor of enzyme Xanthene oxidase whichnormally converts Xanthene into Uric acid

Addition of excess of normal [S] will reverse this

inhibition


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ENZYME INHIBITION

NON COMPETITIVE INHIBITION Inhibitor binds on separate site on enzyme

therefore no competition with substrate. Vmax isreduced and no change in Km

Inhibitor can bind with either free enzyme orenzyme substrate complex and in both casesrender these inactive

Lead poisoning is an example of this inhibitionand it inhibits enzyme Ferrochelatase whichadds iron molecule to the centre of porphyrinring in the synthesis of Hemoglobin


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IRREVERSIBLE INHIBITIONPermanent covalent linkage with enzyme rendering it

irreversibly inhibited

Diisopropyl phospho fluoride (DIPF) Iodoacetamide

Heavy metal [Ag+ Hg+2], Silver, Mercury

Oxidizing agents Covalent linkage with enzyme: inactivation of

enzyme

Kinetics are same as of non competitive inhibition,

therefore difficult to distinguish between the two Examples are insecticides which act as enzyme

poisons for the insects & disinfectants used formicro-organisms


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CO-FACTORS OF ENZYMESENZYMES CO FACTORS

CatalasePeroxidaseCytochrome oxidase

IronFe2+ or Fe3+

Cytochrome oxidase Copper : Cu+2

Carbonic anhydrase alcohol dehydrogenase Zinc : Zn2+

HexokinaseGlucose-6-phosphatasePyruvate kinase

MagnesiumMg2+

Arginase Manganese Mn2+

Pyruvate kinase Potassium K+

Urease Nickel N 2+

Glutathione Peroxidase Selenium : Se


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COENZYMES

Heat stable, low mol wt organic compoundsnon-covalently linked with enzymes can beseparated. APO + CO = Holoenzyme

If covalently Linked to apoenzymes =

prosthetic groupAct as intermediate or ultimate acceptor in

group transfer

D-G + A A-G + DEnzymeCo-Enzyme

D ACo-En-


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COENZYMES

CO ENZYMESFOR TRANSFEROF H+

COENZYMES FOR TRANSFEROF OTHER GROUPS

NAD, NADP SUGAR PHOSPHATESFMN, FAD THIAMINE PYROPHOSPHATE

TPP, PYRIDOXAL PHOSPHATE

LIPOIC ACID FOLATE AND COBAMIDE (VITB12), BIOTIN

COENZYME, Q LIPOIC ACID


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CO-ENZYMES

REDUCTION OF NAD+ TO NADH.H+Lactic acid + NAD Pyruvic acid + NADH-H+

Malic acid + NAD Oxalo acetic acid +

NADH -H+Glucose-6-phosphate + NADP 6-Phosphoglucon-

olactone +NADPH-H+REDUCTION OF FAD OR FMN TO FADH2 OR FMNH2FMN is co enzyme for Cytochrome C oxidase, L.Amino

acid dehydrogenaseFAD is co-enzyme for xanthene oxidase acyl-CoA

dehydrogenase

LDH

Malic dehydrogenase

G-6-P.D


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CO-ENZYMES

Thiamine pyrophosphate:

Co-enzyme for oxidative decarboxylation for ketoacids

Pyruvate Acetyl CoA

Pyruvate +TPP Acetalaldehyde -TPP

complex+Co2

Alpha ketogluterate+6 CoA-SH Succinyl

CoA + Co2

Ribose-5 Po4 + Xylulose-5-Po4 Sedoheptulose 7-Po4 +3 phosphoglyceraldehyde

Pyruvate dehydrogenase

Pyruvate decarboxylase

-ketogluteratedehydrogenase

Transketolase

CoANAD NADH-H+

NAD NADH-H+


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CO-ENZYMESBiotin

Part of multiunit enzymes causing carboxylation reactions. Acts ascarrier of CO2

Acetyl CoA+HCo3 + ATP Malonyl-CoA

Pyruvate+ HCo3 + ATP Oxaloacetate+

ADP+Pi

NH4 + HCo3 + 2ATP CarbamoylPO4 +2 ADP+ 2 Pi

Synthesis of Purines and Pyrimidines

AcetylcarboxylaseEnz-Biotin-COO- Enz-Biotin

Pyruvate carboxylase.Biotin

Carbamoyl Po4.Synthetase -

Biotin


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CO-ENZYMESAscorbic acid (Vitamin C) Strong reducing agent

Required for hydroxylation of proline into hydroxyproline forsynthesis of collagen

Conversion of tyrosine into dopamine and into catecholamines(adrenaline and noradrenalin)

Bile acid formation

Conversion of cholesterol into 7-hydroxylcholesterol

Maintain metallic co-factors like Cu+ in Monooxygenases and Fe indioxygenases in reduced form

Conversion of cholesterol into steroid hormone in adrenal cortex

Absorption of iron by reducing into reduced form which is can beeasily absorbed

Acts as antioxidant in GIT by preventing formation of nitrosaminesduring digestion


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CO-ENZYMES Folic acid

Active form is tetrahydrofolate which acts as singlecarbon carrier for synthesis of various compounds likepyrimidines and purines e.g. conversion of dUMP

(deoxyuridylate) into dTMP (deoxythymidylate)

Vitamin B12

Acts as co-enzyme in groups rearrangements inisomerases e.g. conversion of methyl malonyl CoA intosuccinyl-CoA by enzyme methylmalonyl-CoA mutase

Converts homocystein into methionine

Act as maturation factor for RBCs


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Action of enzyme

(Anabolic reaction)

enzyme

substrate

enzyme

product

enzyme-substrate

complex

enzyme-product

complex


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Action of enzyme

(catabolic reaction)

products

enzyme

enzyme-product

complex

enzyme

substrate

enzyme-substrate

complex


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Lock and key hypothesis

Substrate

Enzyme

product

product


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Lock and key hypothesis

SHAPES

DONT

MATCH


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Enzyme Action:

Induced Fit Model Enzyme structure flexible, not rigid

Enzyme and active site adjust shape tobind substrate

Increases range of substrate specificity

Shape changes also improve catalysisduring reaction


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Enzyme Action:

Induced Fit Model

E + S ES complex E + P

S

P

P

SS


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ENZYME SUBSTRATE BINDING ANDSPECIFICITY

COMPLEMENTARITYOF STRUCTURES

STERIC, CHARGE

NEUTRALITY ANDHYDROGEN BONDFACTORS

ATP TO MYOSIN, Kd =

10-13 M

REGULATION OF ENZYME


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REGULATION OF ENZYMEACTIVITY

There are six different ways

1.Allosteric inhibition

2.Activation of latent enzyme(Proenzyme)

3.Compartmentation of metabolic pathway

4.Control of enzyme synthesis

5.Enzyme degradation6.Isoenzyme


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ALLOSTERIC REGULATION

Low molecular wt allosteric effectors structurallynot similar to substrate

E1 E2 E3A B C D

Bind at sites other than active site leading tofeed back inhibition

Usually product or last small molecule beforemacromolecules in biosynthesis


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PROENZYMES

Inactive enzymes initially secreted as large molecules, activesite not exposed

Pepsinogen HCl Pepsin

Prochyomotrypsin Proteolysis Chymotrypsin

1 245 1 245

Chymotrypsin

Trypsinogen

Enteropeptidase

1 15 16 245 7 245

Trypsin

Trypsin active form

113 16 146 149245 Chymotrypsin active


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PROENZYMES

Required for control of catalytic activity ofenzymes so that catalytic activities only occur

when requiredPancreatic enzymes if all the time active auto

digestion of pancreasBlood clot lysis enzymes only active when blood

clot is formed


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COMPARTMENTATION

The synthetic(anabolic) & breakdown(catabolic) pathways are operative indifferent cellular organelles to achieve

maximum economy. For instance,enzymes for fatty acid synthesis arefound in the cytosol where as enzymesfor fatty acid oxidation are present in the

mitochondria.

CONTROL OF ENZYME


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CONTROL OF ENZYMESYNTHESISSynthesis of enzyme(protein) is

regulated by genes.


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ENZYME DEGRADATION

There is a lot of variability in the halflives of individual enzymes, enzyme withlong half life is usually sluggish in its

catalytic activity. In general, the key & regulatory enzyme

are most rapidly degraded.


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CREATININE KINASE (CK): 3ISOENZYMES

CK1 BB OCCURS IN

BRAIN,SMOOTH

MUSCLES of GIT AND

URINARY TRACT

CK2 MB MYOCARDIUM (35

%), SK MUSCLE (5%)

IN ACUTE MI

CK3 MM CK3 MM IN SK

MUSCLES

CREATININE KINASE


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LACTATE DEHYDROGENASE: 5ISOENZYMES

LDH 1 HHHH Occurs in myocardium (aerobictissues) in acute MI

LDH 2 HHHM In acute leukemia

LDH 3 HHMM In acute leukemia

LDH 4 HMMM Occurs in muscle and liver (anaerobic tissues)

LDH 5 MMMM Occurs in muscle and liver (anaerobic tissues) in liver

diseases

ENZYME PATTERN IN


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ENZYME PATTERN INDISEASESEnzymes in myocardial infarction

The enzymes namely creatinephasphokinase(CPK),aspartate

transaminase(AST) & lactatedehydrogenase(LDH) are important in thediagnosis of MI.


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DIAGNOSTICALLY IMPORTANTENZYMES

ENZYMES PRINCIPALSOURCE

PRINCIPALCLINICAL USE

ACID

PHOSPHATASE

PROSTATE,

RBC

CARCINOMA OF

PROSTATE

ALT (ALANINE

TRANSAMINASE)

LIVER, SK

MUSCLE,

HEART

HEPATIC

PARENCHYMAL

DISEASE

AST (ASPARTATETRANSAMINASE) HEART, LIVER,SK MUSCLE,

KIDNEY, RBCs

MYOCARDIALINFARCTION,

HEPATIC

DISEASE


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ENZYMES PRINCIPAL

SOURCE

PRINCIPAL

CLINICAL USE

ALDOLASE SK MUSCLE,

HEART

MUSCULAR

DYSTROPHIES

ALKALINE

PHOSPHATASE

LIVER, BONE,

INTESTINE,

PLACENTA,

KIDNEYS

BONE,

HEPATOBILIARY

DISEASE

AMYLASE SALIVARY

GLANDS,

PANCREAS,

OVARIES

PANCREATIC

DISEASE


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ENZYMES PRINCIPAL SOURCE PRINCIPAL CLINICAL

USE

CREATINE KINASE SK MUSCLE, HEART,

BRAIN, SM-MUSCLE

MYOCARDIAL

INFARCTION MUSCLE

DISEASE

CHOLINE

ESTRASE

LIVER RGANOPHOSPHORUS

INSECTISIDE

POISONING, HEPATIC

DISEASE

GAMA-GLUTAMYL

TRANSFERASE

LIVER, KIDNEYS ALCOHALIC

HEPATOBILIARY

DISEASE


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DIAGNOSTICALLY IMPORTANT

ENZYMESENZYMES PRINCIPAL

SOURCE

PRINCIPAL CLINICAL

USE

LACTATE DEHY-

DROGENASE

HEART, LIVER,

SK MUSCLE,RBCs,

PLATELETS,

LYMPH NODES

MYOCARDIAL

INFARCTION,HEPATIC DISEASE

GLUTAMATE DE-HYDROGENASE LIVER, HEPATICPARANCHYMAL

DISEASE

ISOCITIRIC DEH-

YDROGENASE

LIVER --DO--


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ENZYMES PRINCIPAL

SOURCE

PRINCIPAL

CLINICAL USE

5-NUCLEOTIDASE LIVER HEPATOBILIARY

DISEASE

GLUCOSE-6-

PHOSPHATE DE-

HYDROGENASE

LIVER HEMOLYTIC

DISORDERS

LIPASE PANCREAS ACUTEPANCREATITIS

SORBITOL DEH-

YDROGENASE

LIVER LIVER

PARENCHYMAL

DISEASE


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Enzyme in muscle disease

increased level of CPK, aldolase AST.

Enzyme in liver disease

1.Alanine transaminase

2.Aspartate transaminase

3.LDH


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Enzymes in cancerincrease in the serum acid phosphatase isspecific for the detection of prostatic carcinoma.


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thousands ofdiseases


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Enzymes are required to

sustainhealth.

Coolege of veterinary & animal sciences, Bikaner


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Coolege of veterinary & animal sciences, Bikaner

Thankyou


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enzyme by cvas,bikaner boys

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