Title: Enzymes%20as%20diagnostic%20
1Enzymes as diagnostic therapeutic tool
- Prepared by Shaikh Abusufyan
2Objectives
- List the clinically important enzymes and
isoenzymes. - State which enzymes and isoenzymes are found in
which tissues - Use of enzymes as diagnostic therapeutic tool
-
3Enzymes
- 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
4Measurement 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
5Information 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
6Enzymes 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
7Measurement 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
8LACTATE 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 -
9Isoenzyme 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
10CREATINE 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
11Isoenzyme 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
12ALANINE 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
13ALANINE 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
14ENZYMES AS A DRUG TARGET
15Renin
- Renin
- Enzyme released by Juxtaglomerular cells of the
kidney - Maintain the BP.
- Role-
- Conversion of angiotensinogen to
angiotensin- I - Increases the
BP
16ACE
- ACE
- Enzyme relesed by Adrenal cortex of the kidney
- Role
- Conversion of angiotensin- I to angiotensin- II
- Increases the BP
17 18Monoamine 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.
21cholinesterase
- 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)
24HMG 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
25Cyclo-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.
26Cyclo-oxygenase (COX)...
- - CoX inhibitores are used as antiinflammatory
- - Eg Diclofenac, Cilicoxif ect
27lanosterol 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.
28lanosterol 14-a-demethylase
- - lanosterol 14-a-demethylase inhibitor
Imidazoles (Antifungal)
29Squalene 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
30Dihydrofolate 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)
32Thymidylate synthase
- Responsible for synthesis of thymidylate
- Inhibitor of Thymidylate synthase
- - 5-Fluorouracil 5-fluorodeoxyuridine (cancer)
33HIV Reverse Transcriptase
Retrovirus Reverse
transcriptase (Viral
RNA dependent DNA polymerase)
DNA copy of the viral RNA
34HIV 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)
38SUMMARY
- 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.
40Thank you