Isoenzymes Overview and Examples
29 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which LDH isoenzyme is predominantly found in the heart?

  • LDH-1 (correct)
  • LDH-3
  • LDH-4
  • LDH-2

    • What is the adaptive significance of glucokinase, the glucose sensor in the pancreas?

  • Regulates blood glucose levels and prevents hyperglycemia after meals. (correct)
  • Ensures survival by maintaining energy production under low glucose conditions.
  • Acts as a glucose sensor in the pancreas and regulates glycogen synthesis in the liver.
  • Provides a constant supply of glucose-6-phosphate for energy production in essential tissues.

    • What is the clinical relevance of hexokinase deficiency?

  • Causes nonspherocytic hemolytic anemia due to insufficient energy in red blood cells. (correct)
  • Ensures survival by maintaining energy production under low glucose conditions.
  • Associated with MODY (Maturity-Onset Diabetes of the Young), affecting blood glucose regulation.
  • Provides a constant supply of glucose-6-phosphate for energy production in essential tissues.

    • Which LDH isoenzyme is mostly present in skeletal muscles?

    <p>LDH-5 (C)</p> Signup and view all the answers

    How many subunits does the lactate dehydrogenase (LDH) enzyme have?

    <p>4 (B)</p> Signup and view all the answers

    Which enzyme type has the highest affinity for pyruvate?

    <p>LDH-1 (C)</p> Signup and view all the answers

    What is the primary physiological role of LDH-5?

    <p>Converts pyruvate to lactate in anaerobic tissues (C)</p> Signup and view all the answers

    Which LDH isozyme is primarily expressed in the lungs?

    <p>LDH-3 (C)</p> Signup and view all the answers

    What type of subunits compose LDH-2?

    <p>3 heart and 1 muscle subunit (C)</p> Signup and view all the answers

    Which LDH isozyme is best suited for anaerobic conditions?

    <p>LDH-5 (A)</p> Signup and view all the answers

    Which LDH enzyme has a moderate affinity for pyruvate?

    <p>LDH-3 (C)</p> Signup and view all the answers

    What type of conditions does LDH-1 operate best under?

    <p>Aerobic conditions (B)</p> Signup and view all the answers

    Which organ is primarily associated with the expression of LDH-5?

    <p>Liver (D)</p> Signup and view all the answers

    What defines isoenzymes?

    <p>Structurally distinct forms of the same enzyme that catalyze the same reaction (C)</p> Signup and view all the answers

    Which characteristic do isoenzymes NOT differ in?

    <p>Catalyzed chemical reaction (C)</p> Signup and view all the answers

    How do hexokinase and glucokinase differ in terms of affinity for glucose?

    <p>Glucokinase has a high Km, indicating low affinity (A)</p> Signup and view all the answers

    What is a key feature of isoenzymes regarding tissue specificity?

    <p>Different isoenzymes are expressed in specific tissues (D)</p> Signup and view all the answers

    What distinguishes the regulatory mechanisms of isoenzymes?

    <p>Isoenzymes differ in sensitivity to allosteric effectors and inhibitors (D)</p> Signup and view all the answers

    Which function is associated with hexokinase?

    <p>Inhibited by glucose-6-phosphate (D)</p> Signup and view all the answers

    In which condition is glucokinase primarily active?

    <p>At high glucose concentrations postprandial (C)</p> Signup and view all the answers

    Which of the following best describes the Km value of hexokinase?

    <p>Low Km, indicating high affinity for glucose (B)</p> Signup and view all the answers

    What does a flipped LDH profile generally indicate?

    <p>Myocardial injury (B)</p> Signup and view all the answers

    In healthy individuals, which LDH isoenzyme is most abundant?

    <p>LDH-2 (B)</p> Signup and view all the answers

    How does LDH-1 change after a myocardial infarction?

    <p>It increases significantly. (B)</p> Signup and view all the answers

    Which enzyme plays a crucial role in energy metabolism in muscle and cardiac tissues?

    <p>Creatine kinase (A)</p> Signup and view all the answers

    What condition is NOT typically associated with a flipped LDH profile?

    <p>Chronic respiratory diseases (D)</p> Signup and view all the answers

    What does creatine kinase catalyze the conversion of?

    <p>Creatine phosphate and ADP to creatine and ATP (A)</p> Signup and view all the answers

    Which LDH isoenzyme is primarily found in the heart?

    <p>LDH-1 (C)</p> Signup and view all the answers

    What is a primary function of creatine kinase in cardiac muscle?

    <p>Maintain ATP levels for ion gradients (C)</p> Signup and view all the answers

    Study Notes

    Isoenzymes

    • Isoenzymes (or isozymes) are different forms of the same enzyme, structurally distinct but catalyzing the same chemical reaction.
    • They differ in amino acid sequence and physicochemical properties (e.g., pH stability, electrophoretic mobility).
    • Key features include:
      • Tissue specificity: Different isoenzymes are expressed in different tissues, enabling tailored metabolic regulation.
      • Kinetic properties: Isoenzymes vary in substrate affinity (Km) and reaction velocity (Vmax).
      • Regulatory mechanisms: Isoenzymes differ in sensitivity to allosteric effectors or inhibitors.

    Examples of Isoenzymes and Their Significance

    • Hexokinase and Glucokinase:

      • Hexokinase: Ubiquitous, low Km, high affinity, inhibited by product (glucose-6-phosphate), active at low glucose.
      • Glucokinase: Primarily in liver and pancreatic beta cells, high Km, low affinity, active at higher glucose concentrations, not inhibited by glucose-6-phosphate.
      • Function in glucose regulation.

    • Lactate Dehydrogenase (LDH):

      • Tetrameric enzyme with (muscle) M and (heart) H subunits.
      • Different LDH isoenzymes (e.g., LDH-1, LDH-2, LDH-3, LDH-4, LDH-5) are formed by various combinations of these subunits.
      • Isozyme profiles can be diagnostic, indicating tissue damage (e.g., myocardial infarction, hemolysis).
      • Flipped LDH profile: a possible clue for a heart attack or other conditions affecting tissue degradation.

    • Creatine Kinase (CK):

      • Catalyzes the reversible conversion of creatine phosphate and ADP to creatine and ATP, supporting energy production in muscles, brain, and heart.
      • Three isoenzymes: CK-MM (muscle), CK-MB (cardiac), and CK-BB (brain).
      • CK-MB is a specific marker for myocardial infarction.

    • Alkaline Phosphatase (ALP):

      • Involved in dephosphorylation, active in alkaline environments.
      • Different tissue-specific isoenzymes (bone-specific, liver, intestinal, placental, germ cell) allowing for differential diagnosis.
      • Elevated levels might indicate bone diseases or liver disorders.

    Detection Methods

    • Electrophoresis separates isoenzymes based on charge and size.
    • Immunoassays utilize specific antibodies to detect and quantify isoenzymes.
    • Spectrophotometry measures enzyme activity through detecting absorbance changes.
    • Chromatography separates isoenzymes based on their physicochemical properties.
    • Heat inactivation tests differentiate isoenzymes based on their thermal stability.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Lecture 7 - Isoenzymes 2024/25

    Description

    This quiz delves into the fascinating world of isoenzymes, highlighting their structural distinctions and functional significance in metabolic regulation. Key isoenzymes such as hexokinase and glucokinase are compared based on their tissue specificity and kinetic properties. Test your understanding of these important biochemical concepts!

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser