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    ClinicalEnzymology

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    Enzymes are the protein catalysts that increase the rate of specific

    chemical reaction in the body.

    Enzymes are found in small amounts mainly within cells ,clotting

    factors and digestive enzymes function naturally after secretion:

    - Plasma specificThrombin- Secreted- Lipase, Amylase

    - Intracellular- transaminases, creatine kinase

    Injury or death of tissues can cause the release of tissue-specific

    enzymes into the bloodstream.

    Elevated enzyme levels are often indicators of tissue problems, and

    are used in the diagnosis of diseases.

    Enzyme activities in the body fluids are altered by pathological

    rocesses so its measurement is used for disease investi ation.

    INTRODUCTION

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    All known enzymes are proteins.

    They are high molecular weight compounds made up principally

    of chains of amino acids linked together by peptide bonds.

    Enzymes can be denatured and precipitated with salts, solvents

    and other reagents.

    They have molecular weights ranging from 10,000 to 2,000,000.

    Many enzymes require the presence of other compounds -

    cofactors - before their catalytic activity can be exerted.

    This entire active complex is referred to as the HOLOENZYME;

    i.e., APOENZYME (protein portion) plus the COFACTOR

    (coenzyme, prosthetic group or metal-ion-activator) .

    Chemical Nature of Enzymes

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    Apoenzyme + Cofactor = Holoenzyme

    The Cofactor may be:

    1 A coenzyme - a non-protein organic substance

    which is dialyzable, thermostable and looselyattached to the protein part.

    2 A prosthetic group - an organic substance which

    is dialyzable and thermostable which is firmlyattached to the protein or apoenzyme portion.

    3 A metal-ion-activator - these include K+, Fe++,

    Fe+++, Cu++, Co++, Zn++, Mn++, Mg++, Ca++, and

    Chemical Nature of Enzymes contd.

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    Enzymes can be classified by the kind of chemical reaction

    catalyzed.A. Addition or removal of water :

    1. Hydrolases - these include esterases, carbohydrases, nucleases,

    deaminases, amidases, and proteases

    2. Hydrases such as fumarase, enolase, aconitase and carbonic

    anhydrase

    B. Transfer of electrons :

    1. Oxidases

    2. Dehydrogenases

    Classification of Enzymes :

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    Classification of Enzymes contd. C. Transfer of a radical:

    1. Transglycosidases - of monosaccharides

    2. Transphosphorylases and phosphomutases - of a phosphategroup

    3. Transaminases - of amino group

    4. Transmethylases - of a methyl group

    5. Transacetylases - of an acetyl group

    D. Splitting or forming a C-C bond:

    1. Desmolases

    2. Changing geometry or structure of a molecule

    3. Isomerases

    E. Joining two molecules through hydrolysis ofpyrophosphate bond in ATP or other tri-phosphate

    1. Ligases

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    One of the properties of enzymes that makes them so

    important as diagnostic and research tools is the specificity

    they exhibit relative to the reactions they catalyze.

    Greater specificity is achieved in three ways:

    1. Interpreting investigations in the light of clinical features

    2. Test pattern recognition

    3. Isoenzyme determination:

    - ASTmay be due toMIorHepatitis so, itmakesconfusion in diagnosis to be confirmed by LDH levels.

    - ALP inCholestasis & bone diseases :- Differentiated by bilirubin & transaminase levels inCholestasis .

    - Confirmed by GGT in Cholestasis.

    Specificity of Enzymes :

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    Specificity of Enzymes contd.In general, there are four distinct types of specificity:

    Absolute specificity - the enzyme will catalyze only onereaction.

    Group specificity - the enzyme will act only on molecules

    that have specific functional groups, such as amino,phosphate and methyl groups.

    Linkage specificity - the enzyme will act on a particular type

    of chemical bond regardless of the rest of the molecularstructure.

    Stereochemical specificity - the enzyme will act on a

    particular steric or optical isomer.

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    Rate of entry into blood

    Serum enzyme activity

    Rate of removal

    Inhibition

    Rate of synthesisMass of enzymeProducing tissue

    Tissue damage

    ClearanceInactivation

    Factors affecting serum enzyme activity

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    I- Rate of entry of enzymes into blood is affected by:

    aRate of synthesisof enzyme:- Biliary obstruction hepatobiliary tree enzymes- Drugs:Anticonvulsant drugs ( Phenobarbital & phenytoin) synthesis of enzymes by the hepatocytes

    b- Mass of enzyme producing cells as in:

    - alkaline phosphatase: ( in active growth , Pagets disease.and in 3rd trimester pregnancy).

    - acid phosphatase ( in cancer prostate).c- Necrosis orCell damage as in:

    - Hepatitis transaminases- Myocardial infarction CK- Stored blood LDH

    Factors affecting Serum enzyme activities-1

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    II-Enzyme inhibitors:- Little effect on enzyme values determined in the lab.

    - Organophosphorus poisoning irreversible inhibition ofcholinesterase.

    III- Clearance of enzymes:

    - Breakdown by Proteases and removal by the reticuloendothelial

    system.

    - Renal excretion of small molecular enzymes e.g.Amylase

    Factors affecting Serum enzyme activities-2

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    Schematic diagram showing the effect of temperature on rate

    of nonenzyme-catalyzed and enzyme catalyzed reactions.

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    Enzymes have anactive site- a cleft into

    which substrate molecules fit

    The active sitecontains amino acids that:

    - Attract the substrate

    -

    Assist in the chemical reactions that convertssubstrate to product

    How does an enzyme work?

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    1) E + S ES. Enzyme and Substrate collide.

    Substrate binds to active site of enzyme.

    A transition state forms where the structure of the substrate is

    altered.

    2) ES EP. Enzyme catalyses the conversion of substrate to Product.

    Both substrate and product remain in active site.

    3) EPE + P. Product is released from active site.

    Sequence of events in enzyme catalyzed reaction

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    ISOENZYMES

    Catalyze the same reaction

    Two or more polypeptide chains

    Different polypeptide chains are products ofdifferent genes

    Differ in AA sequence and physical properties

    May be separable on the basis of charge Are tissue specific

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    Aminotransferases:

    ALT

    AST

    GGT

    ALT and AST :

    1. Pyridoxal dependent2. Indicates Hepatitis, Myocardial infarction:

    - Elevations take > 4 hours to develop, last 4 days

    - ALT elevation lasts longer than AST

    - AST elevations are higher than ALT

    - Elevations occur in most definite infarctions

    3. Skeletal muscle damage

    4. Hemolysis

    5. Pancreatitis

    Isoenzymes and multiple forms

    i f

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    GGT

    Hepatobiliary enzyme - highly inducible in 75% of the

    population

    Highest increases in intra or posthepatic biliary

    obstruction

    Higher and more persistent increases than AlP (Alkaline

    Phosphatase)

    Isoenzymes and multiple forms

    Di ill i h i i f I

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    Diagram illustrating the origin of Isoenzymes

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    Transaminase activities in human tissues,

    relative to serum as unity

    AST ALT

    Heart 7800 450

    Liver 7100 2850

    Skeletal Muscle 5000 300

    Kidney 4500 1200

    Pancreas 1400 130

    Spleen 700 80Lung 500 45

    Erythrocytes 15 7

    Serum 1 1

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    Diagnostic Enzyme Analysis

    Cellular/Plasma specific activities of various enzymes:

    Tissue AST ALT LDH CK

    (GOT) (GPT)

    Heart 8000 400 1000 10000

    Liver 7000 3000 1500

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    LDH-Lactate Dehydrogenase in MI

    LDH is a tetramer of two non-identical subunits (LDH5(M4),LDH4(M3H), LDH3(M2H2), LDH2(MH3), LDH1(H4)

    ENZYMES OF CLINICAL INTEREST

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    Acid phosphatase (ACP)

    Amylase (AMS) Alanine aminotransferase (ALT)

    Alkaline phosphatase (ALP)

    Aspartate aminotransferase (AST)

    Creatine kinase (CK)

    Gamma-glutamyltransferase (GGT)

    Glucose 6-phosphate dehydrogenase (G6PD)

    Lactate dehydrogenase (LDH or LD)

    Lipase (LPS)

    Plasma cholinesterase

    ENZYMES OF CLINICAL INTEREST

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    Diagnostically Important Enzymes 1/3

    Principle Clinical

    Applications

    Principal SourcesEnzyme

    Carcinoma of prostateProstate, erythrocytesAcid

    Phosphatase (ACP)

    Hepatic parenchymal

    disease

    Liver, Skeletal muscle,

    Heart

    Alanine

    aminotransferase(ALT)

    Muscle diseaseSkeletal muscle, heartAldolase

    Bone diseases,

    hepatobiliary diseases

    Liver, bone, intestinal

    mucosa, placenta,kidney

    Alkaline

    Phosphatase (ALP)

    Pancreatic diseasesSalivary glands,

    pancreas, ovariesAmylase(AMS)

    Myocardial infarction,

    hepatic parenchymal

    Liver, skeletal muscle,

    heart, kidney,Aspartate

    aminotransferase(AST)

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    Diagnostically Important Enzymes 2/3

    Principle Clinical

    Applications

    Principal SourcesEnzyme

    Organophosphorus

    insecticide poisoning,

    suxamethonium

    sensitivity, hepaticparenchymal diseases

    LiverCholinesterase

    Myocardial

    infarction, muscle

    diseases

    Skeletal muscle,

    brain, heart, smooth

    muscle

    Creatine kinase(CK)

    Hepatic parenchymal

    disease

    LiverGlutamate

    dehydrogenase

    Hepatobiliary

    disease, alcoholism

    Liver, kidneygamma-GT(GGT)

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    Diagnostically Important Enzymes 3/3

    Principle Clinical

    Applications

    Principal SourcesEnzyme

    Myocardial

    infarction, hemolysis,

    hepatic parenchymal

    disease

    Heart, liver, skeletal

    muscle, erythrocytes,

    platelets, lymph

    nodes

    Lactate

    dehydrogenase(LDH)

    Hepatobiliary diseaseHepatobiliary tract5 Nucleosidase

    Parenchymal hepaticdisease

    LiverSorbitoldehydrogenase

    Pancreatic diseasesPancreasTrypsin(ogen)

    A id h h t (ACP)

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    Found in prostate, bone, liver, spleen, kidney, RBCs

    and platelets

    Primarily used to diagnose prostate cancer . In other prostatic conditions e.g. prostatitis, benignprostatic hypertrophy.

    In other non prostatic conditions e.g. hemolysis, Pagets

    disease, metastatic carcinoma of the breast & Gauchers

    disease.

    Prostate- Specific Antigen(PSA):an enzyme occurs in prostatic

    tissue andin cases of metastatic carcinomaTartarate inhibits the prostatic ACP enzyme while

    Acid phosphatase (ACP)

    Al i i t f (ALT)

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    Alanine aminotransferase (ALT)

    Widely distributed, although the largest amountsfound in the liver.

    Smaller amounts occur in the heart but usually

    remains normal after MI .

    Congestive cardiac failure release from the liverMore specific for liver disease than AST.

    Alk li h h t (ALP)

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    Widely distributed, high concentrations in intestines,

    liver, bone, spleen, placenta and kidney.

    The main sources of serum ALP are the hepatobiliary

    tree and bone disorders.

    Elevated levels during healing of fractures , activegrowth and during the 3rd trimester of pregnancy.

    serum ALP activity in liver disease is mainly due toCholestasis.

    Decreased levels are found in the inherited condition

    Hypophosphatasia which is caused by defective bone

    calcification

    Alkaline phosphatase (ALP)

    Alk li h h t (ALP)

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    Alkaline phosphatase (ALP)Causes of increased serum alkaline phosphatase enzyme activity:

    Physiological :

    Bone disease:

    Hepatobiliary disease:

    Others:

    - Infancy- Puberty

    - Pregnancy

    - Intestinal isoenzymes

    - Hyperparathyroidism- Osteomalacia, rickets

    - Pagets disease of bone

    - Osteomyelitis

    - Hepatitis

    - Cholestasis

    - Cirrhosis

    Carcinoma of the bronchus

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    Alkaline Phosphatase

    Bone Alkaline Phosphatase

    Males

    Females

    4 8 12 16 20 (Years)

    Alk.Phos.units

    A l (AMS)

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    Hydrolases that split complex Polysaccharides.

    - alpha-amylases (1-4 alpha links attacked at random)

    - MW 40,000 - filtered by kidney

    - Ca+2 requiring metalloenzyme

    Sources :

    1. Pancreas (p-type)

    2. Salivary glands (s-type)

    3. Intestinal malignancy

    Amylase (AMS)

    A l (AMS)

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    Clinical Significance : Diagnosis and monitoring of

    pancreatitis1. Acute: - transient increase in activity within 2 - 12 hours

    - returns to normal in 3 - 4 days

    2.Extent of increase (typically 4 - 6 fold) related to probability ofacute pancreatitis.

    3. Serum amylase activitymay be falsely normalin presence ofsevere dyslipidaemia - check urinary amylase.

    4. Serum amylasemay be raised in biliary duct obstruction.

    5. Serum amylase activitymay be normal in chronic pancreatitis.

    6. Amylasemay be raised in pleural effusions and pseudocysticfluids secondary to pancreatitis.

    7. Salivary gland diseases or traumamay raise serum amylaseactivity.

    Amylase (AMS)

    S li E i N l F ti d

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    Salivary Enzymes in Normal Function and

    Abnormal Pathology

    -Amylasenormally present in salivaimportant in digestion

    ______________________________________________

    Lysozyme Hyaluronidase

    Chondrosulfatase

    Aryl Sulfatase

    Neutral Protease

    Collagenases

    Specific activities are increased in

    gingivitis and periodontal disease

    Causes of Hyperamylasemia and Hyperamylasuria

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    1. Pancreatic disease (P-type):

    Pancreatitis:

    - Acute

    - Chronic

    - Complications: Pseudocyst

    Ascites and pleural effusion

    Abcess Pancreatic Trauma, including investigative maneuvers

    Pancreatic carcinoma

    Causes of Hyperamylasemia and Hyperamylasuria

    Causes of Hyperamylasemia and Hyperamylasuria

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    2. Disorders of non-pancreatic origin

    (mechanism unknown) :a-Renal insufficiency (mixed)

    b-Neoplastic hyperamylasemia - usually bronchogenic

    or ovarian (usually S-type)

    c-Salivary gland lesions, e.g. mumps, calculus disease

    (S-type)d-Macroamylasemia (predominantly S-type)

    Causes of Hyperamylasemia and Hyperamylasuria

    Causes of Hyperamylasemia and Hyperamylasuria

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    3. Disorders of complex origin (mechanism unknown or uncertain)

    o Biliary tract disease

    o Intra-abdominal disease (other than pancreatic diseases):

    o Perforated peptic ulcer (P-type)

    o Intestinal obstruction (P-type)

    o Mesenteric infarction (P-type)

    o Peritonitis (mixed; depends on cause)

    o Acute appendicitiso Ruptured ectopic pregnancy (S-type)

    o Aortic aneurysm with dissection

    o Cerebral trauma (type depends on other organ damage)

    o Burns and traumatic shock

    o Postoperative hyperamylasemia (usually S-type)

    o Diabetic ketoacidosis (mixed)

    o Renal transplantation (S-type)

    o Acute alcoholism (mixed)

    o Drugs: - Medicinal opiates (P-type) - Heroin addiction (S-type)

    Causes of Hyperamylasemia and Hyperamylasuria

    A t t i t f (AST)

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    This enzyme is widely distributed in the body.

    Main sources: Heart, liver, skeletal muscle, and kidney.

    Useful in the diagnosis of MI, liver disorders and muscle damage.

    Causes ofserum AST levels:Physiological : Neonates.

    Liver diseases: Hepatitis, hepatic necrosis , cholestasis

    Cardiac disease:Myocardial Infarction.

    Diseases of skeletal muscle:Crush injury,trauma,myopathy

    From Erythrocytes:Hemolysis

    Aspartate aminotransferase (AST)

    C ti ki s (CK)

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    Creatine kinase is associated with ATP regeneration in

    muscle and nervous tissue. Elevated blood levels of CK are used as indicators of MI,

    muscular dystrophy, and stroke.

    CK occurs as a dimer of 2 different subunits, M and B.

    - CK-BB: Brain type.

    - CK-MB: Hybrid type.

    - CK-MM: Muscle type.

    These can be separated by electrophoresis.

    CK-MB is released from cardiac muscle cells after MI.

    Creatine kinase (CK)

    Creatine kinase (CK)

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    BB %MB %MM %

    < 1 80

    MM - skeletal

    muscle

    < 1> 40> 60MB - cardiac

    muscle

    > 95< 30BB - brain

    Creatine kinase (CK)

    A dimer - M and B protein strands which are the products of

    different genes - true isoenzymes.

    5% cutoff by general agreement

    2 of 3 - history, ECG, enzymes

    Gamma glutamyltransferase (GGT)

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    A microsomal enzyme its synthesis induced by ethanol

    and anticonvulsant drugs .

    Found mainly in the kidney and significant amounts in

    liver, brain, prostate, and pancreas .

    Used primarily for diagnosis of hepatobiliary problems . ALT, AST and GGT are the main liver function tests .

    Marked elevation of serum GGT level is seen in

    alcoholic liver disease.

    serum GGTactivity sometimes following MI orcongestive cardiac failure.

    Gamma-glutamyltransferase (GGT)

    Gl cose 6 phosphate deh drogenase (G6PD)

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    First (and control) enzyme for pentose phosphate

    pathway (P.P.P.). Important in production of NADPH + H+, especially in

    RBC.

    NADPH + H+ keeps glutathione reduced.

    Antimalarial drugs are oxidants, and adversely affect

    this system in RBCs.

    Some populations, especially African-Americans, have ahigh frequency of G6PD deficiency.

    If given antimalarial drugs, or fava beans, they develop

    hemolytic anemia.

    Glucose 6-phosphate dehydrogenase (G6PD)

    Lactate dehydrogenase (LDH or LD)

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    Converts pyruvate to lactate (and vice versa) during and

    after anaerobic metabolism.

    LDH occurs as a tetramer of 2 different subunits:

    LD-1 (HHHH) from the heart:

    Elevated after MI.

    LD-2 (HHHM) from the kidney:

    Elevated after renal infarction.

    LD-3 (HHMM) from the lung, spleen and pancreas:Elevated in pulmonary embolism.

    LD-4 (HMMM) and LD-5 (MMMM), both from the liverand skeletal muscle:

    Elevated in injury to liver or skeletal muscle.

    Lactate dehydrogenase (LDH or LD)

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    Lipase (LPS)

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    Breaks down fat into monoacylglycerol and free fatty acids.

    Primarily from the pancreas.

    Used to diagnose acute pancreatitis.

    Pancreatic lipases :

    - A group of enzymes that hydrolyze glycerol esters of long

    chain fatty acids.- Some substrate specificity e.g. LPL (Lipoprotein Lipase).

    - Bile salts are necessary for activity.

    -Almost exclusively used clinically in the investigation of

    pancreatitis.- Increase within 2 - 12 hours of acute attack.

    - May remain elevated for many days .

    - More specific to acute pancreatitis than amylase.

    - Less sensitive to acute exacerbations in chronic pancreatitis.

    Lipase (LPS)

    Plasma cholinesterase

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    Similar to cholinesterase in nervous system, degrades

    acetylcholine (neurotransmitter and hormone).

    Elevated in hepatitis and cirrhosis.

    Also elevated in organophosphate (pesticide) poisoning.

    Degrades succinylcholine, a muscle relaxant given

    during general anesthesia in surgery.

    Some people are deficient in plasma cholinesterase, so

    the normal dose of succinylcholine would kill them

    Therefore, a determination of plasma cholinesterase is

    made prior to major surgery.

    Plasma cholinesterase

    Low Plasma Cholinesterase

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    Low Plasma Cholinesterase

    ExamplesCategory of cause

    Infancy, 3rd Trimester of

    pregnancyPhysiological reasons

    Scoline sensitivity

    (ChE variants)Inherited abnormality

    Acquired abnormality:

    Impaired protein synthesisA) Liver disease

    Organophosphorusinsecticides

    B) Industrial poisoning

    Oral contraceptives, MAO

    inhibitors, Cytotoxic drugsC) Drug effects

    Pancreatic Trypsin

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    A Serine Protease (hydrolyses peptide bondsformed by the carboxyl groups of

    lysine/arginine).

    Inactive Zymogens secreted (Type 1 and 2)

    under the influence of vagus nerve . alpha1-antitrypsin and alpha2-macroglobulin

    protect serum proteins (consider alpha-1 AT

    deficiency).

    Little clinical application in modern practice.

    Pancreatic Trypsin

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    Serum Enzymesin Disease

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    Myocardial Infarction

    Myocardial Infarction ( MI )

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    Myocardial Infarction ( MI ) Necrosis of the myocardium, but not angina pectoris release of

    CK, AST and LDH (HBD) into the circulation.

    CK is the first to rise (activity within 6 h of MI ). Total CK reaches a peak at 24-36 h.

    In uncomplicated cases, CK returns to normal within 3 days.

    Serum AST more slowly ( maximum activity within 48 h) andreturns to normal in 4-5 days.

    No significant elevation in HBD seen for the 1st 24 h (reaches

    maximum at about 3 days & remain for up to 8 days). It is important to consider the timing of sample when interpreting

    test results.

    CK & HBD are useful as early and late indicators of MI, and more

    specific than AST.

    Myocardial Infarction ( MI )

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    Myocardial Infarction ( MI ) CK from skeletal muscle may be following intramuscular

    injection, chest compression for resuscitation or electrical

    defibrillator.

    CK specificity is by measuring CK-MB. HBD activity may bedue to non cardiac factors (hemolysis). Cardiac enzyme measurements are very sensitive indicators of

    MI because it is in over 95% of cases. They are of particular value in the following conditions:

    1. Atypical clinical presentation (absence of chest pain)

    2. If the patient presents some time after a suspected event.

    3. Difficulty in interpreting ECG (Arrhythmia or previous MI).

    4. If further MI is suspected few days of a previous one.

    CK-2 & CK-3 in normal subject and in patient

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    CK 2 & CK 3 in normal subject and in patient

    24 hrs after Myocardial Infarction

    Creatine Kinase isoenzymes in blood

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    Plasma levels following myocardial infarction

    CPK---Creatine Kinase

    LDH---Lactate Dehydrogenase

    HBDH-Hydroxybutyrate

    dehydrogenase

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    Myocardial Infarction :

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    Myocardial Infarction :

    Plasma Enzymes Changes

    Duration ofabnormality

    (days)

    Peak value of

    abnormality(h)

    Abnormalactivity

    detectable(h)

    Enzyme

    1.5 - 312 - 243 - 10CK-MB isoenzyme

    2 - 518 - 305 - 12Total CK

    2 - 620 - 306 - 12AST

    5 - 1430 - 488 - 16Heart-specific LD

    Myocardial Infarction : Plasma enzymes

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    Myocardial Infarction : Plasma enzymes

    vs ECG

    Specificity %Sensitivity %

    10070ECG

    9095PlasmaEnzymes

    Troponin

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    Troponin

    Troponins are a complex ofI, T and C subunits

    uniquely present in striated muscle and regulate thecalcium mediated interaction of actin and myosin.

    Troponin-I has three isoforms:

    sTnI (for fast twitch muscle);

    TnI (for slow twitch muscle) and

    cTnI (for cardiac muscle).

    cTnI levels are elevated in plasma within 4 hr afterinfarction.

    Better test than LDH and CKMB.

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    Muscle DiseasesMuscular Dystrophy

    Toxic Myopathy

    Malignant Hyperpyrexia

    Traumatic Myopathy

    Muscular Dystrophy

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    y p y

    Genetically determined degenerative disorders.

    Duchenne muscular dystrophy is an X-linked recessivedisorder caused by an abnormal dystrophin gene

    (progressive weakness of muscles).

    CK activitiesbefore the onset of clinical symptoms(values >10 times the normal upper level). Serum CK is in 75 % of female carriers.

    Beckers muscular dystrophy is a benign form ofDuchenne MD.

    CK elevated pattern similar to that of Duchenne MD.

    Toxic Myopathy

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    y p y

    Causes:

    - Drugs & chemicals (Alcohol, D-penicillamine, ..etc) generalized myopathy

    - IM injections ( Trauma & Chemical irritation)

    CK activity by narcotic analgesics given in MI. Rapid in body temp, shock& convulsions.(in general Anesthesia Serum CK activity during attacks . Pre-operative CK should be measured in patients with a

    family history of malignant hyperpyrexia.

    Malignant Hyperpyrexia

    Traumatic Myopathies

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    y p

    Muscle trauma (surgery, I.M. injection, etc..) release of enzymes

    High serum CK values occurspost-operatively .

    If MI suspected, CK-MB should be measured.

    Serum CK usuallyreturn to normal within 48 h of

    a single intramuscular injection.

    Vigorous exercise of short duration and prolonged

    moderate exercise serum CK

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    Liver DiseasesHepatic Necrosis

    Hepatitis

    CholestasisJaundice

    Hepatocellular Damage

    Liver Enzymes ( ALT, AST, GGT, ALP, LDH)

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    Measurement of serum enzyme activities for :

    a - Differential Diagnosis of Jaundice.

    b - Monitoring of drug toxicity.

    ALT is more specific than AST.

    Hepatocellular disease has only modest effect on ALP &

    GGT (up to 3 times the upper limit of normal)

    In Cholestasis, Higher values of ALP & GGT due tosynthesis ( the values are 5-10 times the upper normal

    level) .

    y ( , , , , )

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    Bone Diseases- Osteoporosis

    - Osteomalacia

    - Tumors

    - Pagets Disease

    Bone Enzymes - ( Alkaline Phosphatase) ALP

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    ALP enzyme is usually normal in Osteoporosis as

    osteoblastic activity is not increased

    Modest of ALP in Osteomalacia and Rickets Healing fractures Transient of ALP 1ry & 2ry Hyperparathyroidism of ALP

    In Pagets disease of bone of ALP (10 times) 1ry & 2ry bone tumors of ALP (5 times normal)

    y ( p )

    Enzymes in Urine

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    Enzymes in UrineEnzymes appear in Urine from 2 sources:

    - Filtration of plasma

    - Leaking from cells lining the urinary tract

    Amylase is normally detected in urine (small size).

    Indicators of tubular damage:

    - Alkaline phosphatase

    - N-acetyl--glucosaminindase (NAG)

    Enzymes in Hematological

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    Enzymes in Hematological

    Disorders

    Inherited or acquired diseases - Hemolytic diseases

    - Spherocytosis

    - Methemoglobinemia

    G-6-PD deficiency Hemolysison exposure tooxidant drugs as antimalarial drugs (Primaquine) oringestion of fava beans

    Pyruvate kinase , Glutathione synthetase,Hexokinase Defects Hemolysis

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    Thankyou

    Enzymes

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    Enzymes

    Proteins.

    Increase reaction rates by lowering activation

    energy.

    Increase rates by 10

    6

    -10

    12

    . Allow reactions to occur under much milder

    conditions (low temperature, atmospheric

    pressure, around neutral pH).

    Enzymes do not affect the thermodynamic

    properties of a reaction- they do not alter G.

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    Some other Enzymes of Diagnostic Value

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    y g

    Plasma AST in:

    Liver Disease Acute Renal Disease

    Acute Pancreatitis

    Alkaline Phosphatase Liver isoenzyme in:

    Liver cancer and fatty liver

    Bone isoenzyme in: Osteoblastic bone tumors

    Maternal plasma AP up in the third trimester of

    pregnancy

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    Factors affecting serum enzyme concentrations

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    1. Rate of entry

    - tissue damage enzyme synthesis- extent of tissue damage

    - concentration gradient

    - rate of production

    2. Rate of clearance

    - breakdown by proteases

    - removalby reticuloendothelial system

    - renal excretion only foramylase(small molecular weight)

    3. Induction

    4. Proliferation

    Functions of Released Enzymes

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    Functions of Released Enzymes

    Components of boneCollagen, Hyaluronic acid,

    Sulfated glycoproteins, Hydroxyapatite

    Hyaluronic Acid NAG + Glucuronic Acid

    HU

    Sulfated Glycoproteins NAG sulfate + GlucuronicAS, CS Acid

    Acids produced breakdown the hydroxyapatite crystallattice

    Bone Resorption

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    p

    Bone

    Collagen type I Abnormal Hydroxyapatite Crystal

    lattice

    Collagenase type I

    and Chains

    Neutral Proteinase

    Amino acids and peptides