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(Use in alzheimer disease, glaucoma) ... Statins inhibit this enzyme, ... Clinical Enzymology Author: Haiza Last modified by: – PowerPoint PPT presentation

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Title: Enzymes%20as%20diagnostic%20


1
Enzymes as diagnostic therapeutic tool
  • Prepared by Shaikh Abusufyan


2
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

3
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

4
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

5
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

6
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
7
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

8
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

9
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
10
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

11
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
12
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

13
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

14
ENZYMES AS A DRUG TARGET
15
Renin
  • Renin
  • Enzyme released by Juxtaglomerular cells of the
    kidney
  • Maintain the BP.
  • Role-
  • Conversion of angiotensinogen to
    angiotensin- I
  • Increases the
    BP

16
ACE
  • ACE
  • Enzyme relesed by Adrenal cortex of the kidney
  • Role
  • Conversion of angiotensin- I to angiotensin- II
  • Increases the BP

17
  • Renin- agiotensin system

18
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).

19
  • 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).

20
  • 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.

21
cholinesterase
  • 2 main types of cholinesterase r
  • 1. Acetylcholinesterase (AchE) or true
    cholinesterase
  • 2. Butyrocholinesterase (BuChE) or
    Pseudocholinesterase
  • Responsible for degradation of Ach

22
  • 1.Acetylcholinesterase (AchE) or true
    cholinesterase
  • Location
  • - Neurone, ganglia and myoneural junction.
  • Function
  • - Rapidly hydrolyzes acetylcholine

23
  • 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)

24
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

25
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.

26
Cyclo-oxygenase (COX)...
  • - CoX inhibitores are used as antiinflammatory
  • - Eg Diclofenac, Cilicoxif ect

27
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.

28
lanosterol 14-a-demethylase
  • - lanosterol 14-a-demethylase inhibitor
    Imidazoles (Antifungal)

29
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
30
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

31
  • Dihydrofolate reductase Inhibitores
  • - Methrotrexate (anticancer),
  • - pyrimethamine (antiprotozoal, antimalarial),
  • - Trimethoprim (antibacterial)

32
Thymidylate synthase
  • Responsible for synthesis of thymidylate
  • Inhibitor of Thymidylate synthase
  • - 5-Fluorouracil 5-fluorodeoxyuridine (cancer)

33
HIV Reverse Transcriptase

Retrovirus Reverse
transcriptase (Viral
RNA dependent DNA polymerase)
DNA copy of the viral RNA
34
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)

35
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)
36
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)
37
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)

38
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.

39
  • - 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.

40
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