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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Factors affecting enzyme
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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Factors affecting enzyme
activity.Temperature
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Factors affecting enzyme
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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Factors affecting enzyme
activitypH
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Factors affecting enzyme
activity.Enzyme concentration Rate of reaction
continues to increase
with an increase inenzymeconcentration(assuming non
limiting amount ofsubstrate)
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Factors affecting enzyme
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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Factors affecting enzyme
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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Factors affecting enzyme
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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DIAGNOSTICALLY IMPORTANTENZYMES
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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DIAGNOSTICALLY IMPORTANTENZYMES
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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DIAGNOSTICALLY IMPORTANTENZYMES
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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