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Questions and Answers
What is indicated by high levels of alkaline phosphatase (ALP)?
What is indicated by high levels of alkaline phosphatase (ALP)?
Which enzyme is primarily associated with both the heart and liver tissues?
Which enzyme is primarily associated with both the heart and liver tissues?
Which condition is NOT associated with an increase in bone alkaline phosphatase levels?
Which condition is NOT associated with an increase in bone alkaline phosphatase levels?
What does an increase in serum enzyme levels typically indicate?
What does an increase in serum enzyme levels typically indicate?
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What is the result of heat treating a serum sample at 56°C?
What is the result of heat treating a serum sample at 56°C?
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Which enzyme is found predominantly in the prostate?
Which enzyme is found predominantly in the prostate?
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Which enzyme has maximal activity at pH 5.0-6.0?
Which enzyme has maximal activity at pH 5.0-6.0?
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What is the main source of acid phosphatase (ACP) in the body?
What is the main source of acid phosphatase (ACP) in the body?
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Isoenzymes vary primarily in which aspect?
Isoenzymes vary primarily in which aspect?
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Which enzyme is commonly used as a marker for acute pancreatitis?
Which enzyme is commonly used as a marker for acute pancreatitis?
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What does the measurement of serum enzymes help to determine?
What does the measurement of serum enzymes help to determine?
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Which enzyme's levels can be indicative of liver disease and obstructive jaundice?
Which enzyme's levels can be indicative of liver disease and obstructive jaundice?
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Which enzyme is most closely associated with muscle tissue, including cardiac muscle?
Which enzyme is most closely associated with muscle tissue, including cardiac muscle?
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What role does NADH play in the coupled assay for enzyme measurement?
What role does NADH play in the coupled assay for enzyme measurement?
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Which enzymes are primarily measured in relation to liver damage?
Which enzymes are primarily measured in relation to liver damage?
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What is the characteristic of the enzymes measured in diagnostic enzymology?
What is the characteristic of the enzymes measured in diagnostic enzymology?
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What type of phosphatase is primarily used as a marker for prostate disease?
What type of phosphatase is primarily used as a marker for prostate disease?
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Which of the following statements about alkaline phosphatase (ALP) is accurate?
Which of the following statements about alkaline phosphatase (ALP) is accurate?
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Which enzyme is found in the pancreas?
Which enzyme is found in the pancreas?
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What role do enzymes play in biological catalysis?
What role do enzymes play in biological catalysis?
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Which of the following enzymes is most specifically associated with myocardial infarction?
Which of the following enzymes is most specifically associated with myocardial infarction?
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Which enzyme is primarily elevated in conditions of biliary obstruction?
Which enzyme is primarily elevated in conditions of biliary obstruction?
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What is the primary function of aspartate aminotransferase (AST)?
What is the primary function of aspartate aminotransferase (AST)?
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Which enzyme is indicative of liver damage, especially in conditions involving cellular injury?
Which enzyme is indicative of liver damage, especially in conditions involving cellular injury?
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What is a characteristic of isoenzymes?
What is a characteristic of isoenzymes?
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Which enzyme measurement is beneficial in the diagnosis of prostate cancer?
Which enzyme measurement is beneficial in the diagnosis of prostate cancer?
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Which of the following is true regarding Gamma Glutamyl Transferase (GGT)?
Which of the following is true regarding Gamma Glutamyl Transferase (GGT)?
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What is a common condition that results in elevated levels of Lactate Dehydrogenase (LDH)?
What is a common condition that results in elevated levels of Lactate Dehydrogenase (LDH)?
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Which enzyme is considered most significant in the investigation of heart disease?
Which enzyme is considered most significant in the investigation of heart disease?
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What is the correct method for enzyme measurements according to zero order kinetics?
What is the correct method for enzyme measurements according to zero order kinetics?
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What is the significance of the enzyme activity being expressed in International Units (IU)?
What is the significance of the enzyme activity being expressed in International Units (IU)?
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Which lactate dehydrogenase isoenzyme is predominantly found in the myocardium?
Which lactate dehydrogenase isoenzyme is predominantly found in the myocardium?
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In the context of myocardial infarction, which enzyme levels rise first?
In the context of myocardial infarction, which enzyme levels rise first?
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What is a notable biochemical feature of creatine kinase isoenzymes?
What is a notable biochemical feature of creatine kinase isoenzymes?
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Which enzyme is markedly elevated during liver damage and is considered specific for hepatocellular injury?
Which enzyme is markedly elevated during liver damage and is considered specific for hepatocellular injury?
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What role does alkaline phosphatase (ALP) play in diagnosing diseases?
What role does alkaline phosphatase (ALP) play in diagnosing diseases?
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Which characteristic is true for aspartate transaminase (AST) compared to alanine transaminase (ALT)?
Which characteristic is true for aspartate transaminase (AST) compared to alanine transaminase (ALT)?
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Which isoenzyme of creatine kinase is primarily associated with cardiac muscle?
Which isoenzyme of creatine kinase is primarily associated with cardiac muscle?
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What distinguishes lactate dehydrogenase isoenzymes from each other?
What distinguishes lactate dehydrogenase isoenzymes from each other?
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Which of the following conditions do not result in elevated LDH levels?
Which of the following conditions do not result in elevated LDH levels?
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Study Notes
Clinical Enzymology Objectives
- List clinically important enzymes and isoenzymes.
- State the tissues where enzymes and isoenzymes are found.
- Describe plasma enzyme changes in myocardial infarction and liver disease.
- Outline different methods of measuring plasma enzymes.
Enzymes
- Biological catalysts, highly efficient, increasing reaction rates by orders of magnitude (e.g., x10).
- Composed of protein, susceptible to denaturation.
- Specific for specific substrates.
- Partially specific for tissues.
- Enzyme activity measured by the rate of specific reactions they catalyze.
Measurement of Serum Enzymes
- Diagnostic tool for enzymology.
- Enzymes usually intracellular, with low concentrations in blood.
- Release into blood indicates cell damage (death, hypoxia, or intracellular toxicity).
- Quantitative measure of cell/tissue damage.
- Repeated testing is possible.
- Organ specificity exists, but not absolute.
- Most enzymes present in most cells in varying amounts.
Enzymes Routinely Measured
| Enzyme Name | Present In |
|---|---|
| Aspartate Aminotransferase (AST) | Heart and Liver |
| Serum Glutamate-Oxaloacetate Transaminase (SGOT) | Heart and Liver |
| Alanine Aminotransferase (ALT) | Heart and Liver |
| Serum Glutamate-Pyruvate Transaminase (SGPT) | Bone, intestine, and other tissues |
| Alkaline Phosphatase (ALP) | Prostate |
| Acid Phosphatase (ACP) | Liver |
| γ-Glutamyl Transferase (γGT) | Muscle, including cardiac muscle |
| Creatine Kinase (CK) | Heart, liver, muscle, RBC |
| Lactate Dehydrogenase (LDH) | Pancreas |
| α-Amylase |
Isoenzymes
- Catalyze the same reactions but composed of structurally different polypeptides.
- Perform the same catalytic function.
- Variations in isoenzymes can arise from different tissues, providing clues about the site of pathology.
- Isoenzyme variations can differ by enzymatic properties, physical properties (e.g., heat stability), and biochemical properties (e.g., amino acid composition) and immunological reactivities.
Measurement of Enzyme Activity
- Enzyme activity is measured using international units (IU).
- One IU corresponds to the amount of enzyme that catalyzes the conversion of one micromole (µmol) of substrate to product per minute.
Lactate Dehydrogenase (LDH)
- Elevated in myocardial infarction and blood disorders.
- Tetrameric protein with H (heart) and M (muscle) subunits.
- Exists as five different isoenzymes with various combinations of H and M subunits.
Creatine Kinase (CK)
- Dimer made of two monomers.
- Skeletal muscle contains M subunit; brain contains B subunit.
- Three isoenzymes (CK-1, CK-2, CK-3) exist.
Alanine Transaminase (ALT) and Aspartate Transaminase (AST)
- Located primarily in the liver.
- Elevated in blood indicates liver damage (e.g., viral hepatitis).
- ALT more specific for liver damage (hepatocellular damage).
- AST levels increase in myocardial infarction and muscular dystrophy.
Levels of Enzymes in Diseases Involving Liver Damage
- ALT and AST levels rise rapidly in viral hepatitis, often before bilirubin levels increase.
Levels of Enzymes in Myocardial Infarction
- AST and CK rise within 6 hours of acute myocardial infarction.
- Other enzymes (e.g., HBDH, LDH) rise later, remaining elevated for longer periods.
Alkaline Phosphatase (ALP)
- Enzyme group with maximal activity at a pH of 9.0-10.5.
- Found in liver, bone, placenta, and intestines.
- High levels indicate hepatobiliary or bone diseases (e.g., obstruction, rickets).
- Increased in bone diseases like rickets, osteomalacia, neoplastic diseases with bone metastases, and healing fractures.
Acid Phosphatase (ACP)
- Enzyme group with maximal activity between pH 5.0-6.0.
- Found in prostate gland, liver, spleen, and red blood cells (RBCs).
- Primarily present in the prostate gland, making it a biomarker for prostate disease.
Amylase
- Digestive enzyme from the pancreas and salivary glands, breaking down carbohydrates.
- Elevated levels indicate acute pancreatitis and appendicitis.
γ-Glutamyltransferase (γGT)
- Involved in amino acid transport across cell membranes.
- Predominantly found in liver, kidney, and pancreatic biliary ducts.
- Enzyme activity induced by alcohol and certain drugs.
- Elevated in liver diseases (especially obstructive jaundice), alcohol-induced liver disease, and cirrhosis.
Measurement of Enzymes
- Techniques include end-point assays and kinetic assays.
- Enzyme measurements affected by inhibitors or activators.
- Coupled assays often used, utilizing a second enzyme to measure the products of the primary enzyme.
Principle Involved in AST Estimation
- Coupled assay utilizes malate dehydrogenase (MDH) to measure the oxidation of NADH.
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Description
This quiz covers essential concepts in clinical enzymology, including important enzymes and their respective tissues. You'll explore plasma enzyme changes in conditions like myocardial infarction and liver disease, as well as the various methods of measuring enzyme levels in serum. Test your knowledge on the diagnostic significance of enzymes in clinical practice.
