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Questions and Answers
Enzymes can decrease reaction rates by an order of x 10.
Enzymes can decrease reaction rates by an order of x 10.
False
Lactate Dehydrogenase (LDH) is exclusively found in the liver.
Lactate Dehydrogenase (LDH) is exclusively found in the liver.
False
Isoenzymes are enzymes that have the same substrate specificity but differ in structural properties.
Isoenzymes are enzymes that have the same substrate specificity but differ in structural properties.
True
Elevated levels of alkaline phosphatase (ALP) are associated with muscle tissues.
Elevated levels of alkaline phosphatase (ALP) are associated with muscle tissues.
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Aspartate Amino transferase (AST) is only found in the heart.
Aspartate Amino transferase (AST) is only found in the heart.
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The presence of enzymes in serum indicates healthy cellular function.
The presence of enzymes in serum indicates healthy cellular function.
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Enzyme release into the bloodstream can be used as a quantitative measure of tissue damage.
Enzyme release into the bloodstream can be used as a quantitative measure of tissue damage.
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Creatine kinase (CK) is primarily associated with cardiac tissue.
Creatine kinase (CK) is primarily associated with cardiac tissue.
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Serum glutamate-oxaloacetate transaminase (SGOT) is an alternative name for Alanine Amino transferase (ALT).
Serum glutamate-oxaloacetate transaminase (SGOT) is an alternative name for Alanine Amino transferase (ALT).
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Differentiating isoenzymes can provide clues about the site of pathology in the body.
Differentiating isoenzymes can provide clues about the site of pathology in the body.
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Increased levels of acid phosphatase are found in breast cancer.
Increased levels of acid phosphatase are found in breast cancer.
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Isoenzyme patterns can provide information about organ-specific disease.
Isoenzyme patterns can provide information about organ-specific disease.
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AST is primarily associated with pancreatic diseases.
AST is primarily associated with pancreatic diseases.
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Creatine kinase has two isoenzymes: CK-MM and CK-MB.
Creatine kinase has two isoenzymes: CK-MM and CK-MB.
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Lactate dehydrogenase levels can be elevated in liver disease.
Lactate dehydrogenase levels can be elevated in liver disease.
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Alkaline phosphatase is exclusively used for diagnosing bone diseases.
Alkaline phosphatase is exclusively used for diagnosing bone diseases.
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GGT levels are increased due to alcohol abuse.
GGT levels are increased due to alcohol abuse.
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Myocardial infarction can lead to elevated levels of lactate dehydrogenase.
Myocardial infarction can lead to elevated levels of lactate dehydrogenase.
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Enzyme measurements should be performed using first order kinetics.
Enzyme measurements should be performed using first order kinetics.
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High levels of ALP are indicative of intrahepatic obstruction rather than extrahepatic obstruction.
High levels of ALP are indicative of intrahepatic obstruction rather than extrahepatic obstruction.
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Alanine Amino transferase (ALT) is primarily associated with myocardial infarction.
Alanine Amino transferase (ALT) is primarily associated with myocardial infarction.
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The enzyme alkaline phosphatase is derived from osteoblasts and is increased in conditions like rickets and osteomalacia.
The enzyme alkaline phosphatase is derived from osteoblasts and is increased in conditions like rickets and osteomalacia.
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ACID PHOSPHATASE (ACP) has maximal activity at pH levels above 7.0.
ACID PHOSPHATASE (ACP) has maximal activity at pH levels above 7.0.
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The main source of ACP is the spleen, making it a marker for spleen diseases.
The main source of ACP is the spleen, making it a marker for spleen diseases.
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Amylase is primarily used to digest complex carbohydrates and is elevated in acute pancreatitis.
Amylase is primarily used to digest complex carbohydrates and is elevated in acute pancreatitis.
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GGT is involved in amino acid transport and is found mainly in the spleen and lungs.
GGT is involved in amino acid transport and is found mainly in the spleen and lungs.
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Enzyme activity measurements can be affected by the presence of inhibitors or activators.
Enzyme activity measurements can be affected by the presence of inhibitors or activators.
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Bone ALP is heat stable and is not inactivated when serum samples are heated to 56°C.
Bone ALP is heat stable and is not inactivated when serum samples are heated to 56°C.
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Measurement of ALP before and after heat treatment provides an estimation of kidney ALP levels.
Measurement of ALP before and after heat treatment provides an estimation of kidney ALP levels.
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NADH is used as a coenzyme in coupled assays for measuring enzyme activity.
NADH is used as a coenzyme in coupled assays for measuring enzyme activity.
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Lactate dehydrogenase (LDH) exists as four different isoenzymes with various combinations of H and M subunits.
Lactate dehydrogenase (LDH) exists as four different isoenzymes with various combinations of H and M subunits.
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The enzyme activity of creatine kinase is expressed in International units (IU), which corresponds to the amount of enzyme that catalyzes the conversion of one millimole of substrate to product per minute.
The enzyme activity of creatine kinase is expressed in International units (IU), which corresponds to the amount of enzyme that catalyzes the conversion of one millimole of substrate to product per minute.
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Alanine transaminase (ALT) levels increase significantly during muscular dystrophy.
Alanine transaminase (ALT) levels increase significantly during muscular dystrophy.
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In viral hepatitis, the transaminase levels can increase 20-50 times above the normal range before any rise in bilirubin is observed.
In viral hepatitis, the transaminase levels can increase 20-50 times above the normal range before any rise in bilirubin is observed.
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Creatine kinase (CK) is formed entirely from M subunits in the skeletal muscle.
Creatine kinase (CK) is formed entirely from M subunits in the skeletal muscle.
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LDH1, which is made up of H4 subunits, is primarily elevated in skeletal muscle disorders.
LDH1, which is made up of H4 subunits, is primarily elevated in skeletal muscle disorders.
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High levels of alkaline phosphatase (ALP) can be observed in conditions affecting the liver, bone, placenta, and intestine.
High levels of alkaline phosphatase (ALP) can be observed in conditions affecting the liver, bone, placenta, and intestine.
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Aspartate transaminase (AST) is significantly elevated in liver conditions but not in acute myocardial infarction.
Aspartate transaminase (AST) is significantly elevated in liver conditions but not in acute myocardial infarction.
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The H subunit of lactate dehydrogenase (LDH) is primarily found in the skeletal muscle.
The H subunit of lactate dehydrogenase (LDH) is primarily found in the skeletal muscle.
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Enzyme activity is measured to gain insight into various physiological conditions and is important for diagnosing diseases.
Enzyme activity is measured to gain insight into various physiological conditions and is important for diagnosing diseases.
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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 for measuring plasma enzymes.
Enzymes
- Biological catalysts, highly efficient, increasing reaction rates by factors of 10.
- All enzymes are proteins, susceptible to denaturation.
- Specific to substrates.
- Partly tissue-specific.
- Enzyme activity measured by rate of specific reactions catalyzed.
Measurement of Serum Enzymes
- Diagnostic enzymology
- Enzymes normally intracellular, low concentration in blood.
- Enzyme release (leakage) signifies cell damage (death, hypoxia, intracellular toxicity).
- Quantifies cell/tissue damage.
- Relatively noninvasive, allows for repeated tests.
- Organ specificity exists, but not absolute. Most enzymes are present in most cells in varying amounts.
Enzymes Routinely Measured
- 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): Bone, intestine and other tissues
- Acid Phosphatase (ACP): Prostate
- γ-glutamyl Transferase (γ GT): Liver
- Creatine Kinase (CK): Muscle (including cardiac muscle)
- Lactate Dehydrogenase (LDH): Heart, liver, muscle, RBC
- Amylase: Pancreas
Isoenzymes
- Catalyze same reactions, formed from different polypeptides.
- Perform same catalytic function.
- Different isoenzymes arise from different tissues, providing clues to pathology.
- Isoenzymes vary in:
- Enzymatic properties
- Physical properties (e.g., heat stability)
- Biochemical properties (e.g., amino acid composition)
- Immunological reactivities
Measurement of Enzyme Activity
- Expressed in International Units (IU).
- Corresponds to the amount of enzyme catalyzing the conversion of 1 micromole of substrate to product per minute.
Lactate Dehydrogenase (LDH)
- Elevated in myocardial infarction, blood disorders.
- Tetrameric protein with H (heart) and M (muscle) subunits.
- 5 different isoenzymes (combinations of H and M subunits).
- Specific isoenzyme elevations indicate tissue damage.
Creatine Kinase (CK)
- Dimeric enzyme.
- Skeletal muscle contains M subunit, brain contains B subunit.
- Three different isoenzymes.
- Elevated levels indicate muscle damage or CNS disorders.
Alanine Transaminase (ALT) and Aspartate Transaminase (AST)
- Abundantly present in liver, elevated in blood due to leakage from damaged cells.
- Measurements used to diagnose liver disorders.
- ALT elevations are specific for liver damage.
- AST elevations occur in a wider range of conditions.
Levels of Enzymes in Diseases Involving Liver Damage
- Viral hepatitis show rapid rise in transaminases (ALT and AST), even before bilirubin rise.
Alkaline Phosphatase (ALP)
- Enzyme with maximal activity at high pH (9.0-10.5).
- Distributed throughout body, high levels in liver, bone, placenta, and intestine.
- Increased levels indicate hepatobiliary obstruction or bone diseases.
- Derived from osteoblasts; increased in bone diseases.
Acid Phosphatase (ACP)
- Maximal activity at pH 5.0-6.0.
- Present in prostate gland, liver, spleen, and RBCs.
- Prostate gland is major source; useful marker for prostate disease.
Amylase
- Digestive enzyme, digests complex carbohydrates.
- Pancreas and salivary glands.
- Elevated in acute pancreatitis and appendicitis.
γ-glutamyltransferase (γ GT)
- Involved in amino acid transport.
- Found in liver, kidney, and pancreas biliary ducts.
- Enzyme activity induced by drugs and alcohol.
- Elevated levels used to diagnose alcohol-induced liver disease and liver cirrhosis, especially obstructive jaundice.
Measurement of Enzymes
- End-point assay
- Kinetic assay
- Coupled assays frequently used to measure enzyme activity, using a secondary enzyme to measure the reaction of the primary enzyme of interest.
Principle Involved in AST Estimation
- Coupled enzymatic reactions to measure AST activity (using a spectrophotometer to detect changes in the amount of NADH produced).
Summary (page 12)
- Enzymes are biological catalysts.
- Enzymes act on specific substrates.
- Isoenzymes are variations of an enzyme within a tissue.
- Isoenzyme patterns provide clues to specific organ damage.
- Key enzymes for diagnosing heart conditions (CK, LDH, and AST).
- Important enzymes for diagnosing liver conditions (AST, ALT, alkaline phosphatase, and GGT).
- Creatine kinase (CK) has three isoenzymes (CK-MM, CK-MB, and CK-BB).
- Lactate dehydrogenase (LDH) has five isoenzymes.
- Alkaline phosphatase (ALP) assessment in liver and bone conditions.
- Alkaline phosphatase elevated in prostate cancer.
- γ-GT is often increased by alcohol. Measurement using excess substrate (zero-order kinetics)
- Enzymatic activity measurement methods - end-point or kinetic.
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Description
This quiz covers essential concepts related to enzymes, including their reaction rates, localization in tissues, and clinical significance. You'll explore the roles of various enzymes such as Lactate Dehydrogenase, Creatine Kinase, and others in diagnosing diseases. Get ready to test your knowledge on enzyme isoforms and their implications in pathology.
