Enzymes%20as%20diagnostic%20

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Enzymes as diagnostic therapeutic tool

• Prepared by Shaikh Abusufyan
  
  

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Objectives

• List the clinically important enzymes and
  isoenzymes.
• State which enzymes and isoenzymes are found in
  which tissues
• Use of enzymes as diagnostic therapeutic tool

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Enzymes

• Biological catalysis
• Very efficient can increase reaction rates at
  the order of x 10
• All are proteins- so liable to denaturation
• Specific to substrates
• Partly specific to tissues

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Measurement of serum enzymes

• Diagnostic enzymology
• Enzymes are normally intracellular and LOW
  concentration in blood
• Enzyme release (leakage)in the blood indicates
  cell damage (cell death, hypoxia, intracellular
  toxicity)
• Quantitative measure of cell/tissue damage
• Fairly non invasive possible to do repeated tests
• Organ specificity- but not absolute specificity

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Information from enzymes measurements in serum

• Presence of disease
• Organs involved
• Aetiology /nature of disease differential
  diagnosis
• Extent of disease-more damaged cells-more leaked
  enzymes in blood
• Time course of disease

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Enzymes routinely measured
NAME OF THE ENZYME PRESENT IN
Aspartate Amino transferase (AST) Serum glutamate-oxaloacetate transaminase (SGOT) Heart and Liver
Alanine Amino transferase (ALT) Serum glutamate-pyruvate transaminase (SGPT) Heart and Liver
Alkaline Phosphatase (ALP) Bone, intestine and other tissues
Acid Phosphatase (ACP) Prostate
? glutamyl Transferase (? GT) Liver
Creatine kinase (CK) Muscle Including cardiac muscle
Lactate Dehydrogenase (LDH) Heart, liver, muscle, RBC
? Amylase Pancreas
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Measurement of enzyme activity

• Enzyme activity is expressed in International
  unit (IU)
• It corresponds to the amount of enzymes that
  catalyzes the conversion of one micromole (?mol)
  of substrate to product per minute

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LACTATE DEHYDROGENASE (LDH)

• Pyruvate Lactate
  (anaerobic glycolysis)
• LDH is elevated in myocardial infarction, blood
  disorders
• It is a tetrameric protein and made of two types
  of subunits namely H Heart, M skeletal muscle
• It exists as 5 different isoenzymes with various
  combinations of H and M subunits

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Isoenzyme name Composition Composition Present in Elevated in
LDH1 ( H4) HHHH Myocardium, RBC myocardial infarction
LDH2 (H3M1) HHHM Myocardium, RBC
LDH3 (H2M2) HHMM Kidney, Skeletal muscle
LDH4 (H1M3) HMMM Kidney, Skeletal muscle
LDH5 (M4) MMMM Skeletal muscle, Liver Skeletal muscle and liver diseases
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CREATINE KINASE (CK)

• Creatine ATP
  phosphocreatine ADP
• (Phosphocreatine serves as energy reserve
  during muscle
• contraction)
• Creatine kinase is a dimer made of 2 monomers
• Skeletal muscle contains M subunit, Brain
  contains B subunits
• Three different isoenzymes are formed

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Isoenzyme name Composition Present in Elevated in
CK-1 BB Brain CNS diseases
CK-2 MB Myocardium/ Heart Acute myocardial infarction
CK-3 MM Skeletal muscle, Myocardium
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ALANINE TRANSAMINASE (ALT) or SGPT AND ASPARTATE
TRANSAMINASE( AST) or SGOT

• Alanine transaminase (ALT) and Aspartate
  transaminase (AST) enzymes are the most
  abundantly present in the liver
• Elevated in blood as a result of leakage from
  damaged cells
• Measurement of these transaminases is useful for
  the diagnosis of liver diseases

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ALANINE TRANSAMINASE (ALT) AND ASPARTATE
TRANSAMINASE ( AST).......

• In viral hepatitis the enzyme levels are
  increased 20-50 times
• Alanine transaminase (ALT) increase is specific
  for liver damage involving hepatocellular damage
• Aspartate transaminase (AST) is moderately
  increased in Muscular dystrophy and acute
  myocardial infarction

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ENZYMES AS A DRUG TARGET
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Renin

• Renin
• Enzyme released by Juxtaglomerular cells of the
  kidney
• Maintain the BP.
• Role-
• Conversion of angiotensinogen to
  angiotensin- I
• Increases the
  BP

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ACE

• ACE
• Enzyme relesed by Adrenal cortex of the kidney
• Role
• Conversion of angiotensin- I to angiotensin- II
• Increases the BP

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• Renin- agiotensin system

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Monoamine oxidase (MAO)

• It is a membrane-bound mitochondrial enzyme that
  oxidatively deaminates primary amines to
  aldehydes.
• Location
• - liver, kidney, intestine and nervous tissue
• Substrates
• - Catecholamines (dopamine, noradrenaline and
  adrenaline), tyramine, phenylephrine and
  tryptophan derivatives (5-hydroxytryptamine and
  tryptamine).

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• There are 2 type of MAO
• 1. MAO-A
• - It oxidise mainly NA 5-HT
• - Inhibited selectively by v low concentration of
  chlorgyline moclobemide (Antidepressant).

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• MAO-B
• - It oxidizes DA in the brain
• - selectively inhibited by selegiline
  (Antiparkinson).
• Liver contain equal amount of both MAO enzyme
  while brain contain MAO- B.

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cholinesterase

• 2 main types of cholinesterase r
• 1. Acetylcholinesterase (AchE) or true
  cholinesterase
• 2. Butyrocholinesterase (BuChE) or
  Pseudocholinesterase
• Responsible for degradation of Ach

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• 1.Acetylcholinesterase (AchE) or true
  cholinesterase
• Location
• - Neurone, ganglia and myoneural junction.
• Function
• - Rapidly hydrolyzes acetylcholine

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• 2. Butyrocholinesterase (BuChE) or
  Pseudocholinesterase
• Location
• Plasma, RBCs, liver, glia and other organs
• Function
• - hydrolysis of Ach slowly
• The activity of cholinesterase is inhibited by
  anticholinesterase drugs. (Use in alzheimer
  disease, glaucoma)

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HMG CoA reductase

• - It is the rate-limiting enzyme in cholesterol
  biosynthesis.
• - Statins inhibit this enzyme, lowering
  cytoplasmic cholesterol.
• - And used in the treatment of Hyperlipedemia

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Cyclo-oxygenase (COX)

• There are two main isoforms, COX-1 and COX-2.
• - COX-1 is a constitutive enzyme which is
  present in platelets and other cells.
• - COX-2 is an inducible form, which is produced
  in response to cytokine stimulation in areas of
  inflammation.
• - Produces large amounts of prostaglandins
  responsible for inflammation.

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Cyclo-oxygenase (COX)...

• - CoX inhibitores are used as antiinflammatory
• - Eg Diclofenac, Cilicoxif ect

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lanosterol 14-a-demethylase

• - It is a fungal cytochrome-haem P450 enzyme,
• - Responsible for synthesise of ergosterol from
  lanosterole.
• Inhibition of
  enzyme
• disrupts the acyl chains of fungal membrane
  phospholipids,
• increasing membrane fluidity and causes membrane
  leakage and dysfunction of membrane-bound enzymes
  Antifungal activity.

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lanosterol 14-a-demethylase

• - lanosterol 14-a-demethylase inhibitor
  Imidazoles (Antifungal)

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Squalene epoxidase

• It is involved in fungal ergosterol biosynthesis.
• ergosterol
  squaline
• - Inhibition of the enzyme lead to accumulation
  of squaline within the cell
• toxic
  to the organism
• Eg. of squaline epoxidase inhibitor Terbinafine
  (Antifungal)

squaline epoxidase
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Dihydrofolate reductase

• - Responsible for conversion of dihydrofolate to
  tetrahydrofolate
• folic acid synthesis
• - Folic acid is required in the synthesis of
  thymidylate (pyrimidine) and of purine
  nucleotides and thus for DNA synthesis

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• Dihydrofolate reductase Inhibitores
• - Methrotrexate (anticancer),
• - pyrimethamine (antiprotozoal, antimalarial),
• - Trimethoprim (antibacterial)

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Thymidylate synthase

• Responsible for synthesis of thymidylate
• Inhibitor of Thymidylate synthase
• - 5-Fluorouracil 5-fluorodeoxyuridine (cancer)

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HIV Reverse Transcriptase

Retrovirus Reverse
transcriptase (Viral
RNA dependent DNA polymerase)
DNA copy of the viral RNA
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HIV Reverse Transcriptase Inhibitors

• MOA
• -Competitive inhibition of HIV-1 reverse
  transcriptase
• - Incorporated into the growing viral DNA chain ?
  cause termination
• - Most have activity against HIV-2 as well as
  HIV-1.
• - Eg. 3-azido-2,3-dideoxythymidine (AZT)

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IV. Enzymes as drug targets
Enzyme Drug/ Inhibitores/Significant
- Mono amine oxidase Ephedrine,
Amphetamine (MAO)
(Increases the level of catecholamine) - Acetyl
cholinesterase Neostigmine (Used in
glaucoma). - HMG CoA reductase
Lovastatin, Compactin (Inhibit
cholestrol
biosynthesis) - ACE
Enalapril, Captopril (Control the BP)
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IV. Enzymes as drug targets
Enzyme Drug/ Inhibitores/Significant
- Cyclooxygenase Paracetamol
(Non- (COX)
selective NSAIDS), Aspirine

(Antiplateletes)
Cilicoxibe (Selective COX-II

Inhibitores) lanosterol
Imidazoles (Antifungal) 14-a-demethylase
(a fungal cytochrome-haem P450
enzyme) squalene epoxidase
Terbinafine (Antifungal)
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IV. Enzymes as drug targets
Enzyme targeting Drug Dihydrofolate reductase
Antifolates methrotrexate (cancer),
(Folate metabolism) pyrimethamine (protozoa,
malaria)
trimethoprim (bacteria) Thymidylate synthase
5-Fluorouracil (Pyrimidine
metabolism) 5-fluorodeoxyuridine
(cancer) HIV-Reverse transcriptase
3-azido-2,3-dideoxythymidine (AZT) HIV
proteases
Ritonavir, saquinavir (clinical trial phase)

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SUMMARY

• Enzymes are biological catalysts present in every
  cell of the body.
• Isoenzyme patterns can give information about
  organ-specific disease.
• Important enzymes in the investigation of heart
  disease are CK, LDH and AST.
• Important enzymes in the investigation of liver
  disease are AST, ALT, alkaline phosphatase.

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• - Creatine kinase has three isoenzymes CK-MM,
  CK-MB and CK-BB.
• - LDH has five isoenzymes.
• - Increased levels of acid phosphatase are found
  in prostate cancer.

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Thank you