Enzyme Allosteric Regulation
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Questions and Answers

What is the function of ligases?

  • Paste two pieces together (make a chemical bond), uses ATP (correct)
  • Rearrange the order of atoms in a molecule (isomerization)
  • Break a chemical bond without using water
  • Add water across a chemical bond (hydrolysis)

    • Which enzyme type is responsible for breaking a chemical bond by adding water across it?

  • Ligases
  • Lyases
  • Isomerases
  • Hydrolases (correct)

    • Which coenzyme is a building block of Vitamin B1?

  • Thiamine Pyrophosphate (correct)
  • Adenosine Monophosphate
  • Lipoamide
  • CoASH

    • What is the common theme associated with Coenzyme A?

    <p>Sulfur</p> Signup and view all the answers

    Which enzyme type is responsible for rearranging the order of atoms in a molecule (isomerization)?

    <p>Isomerases</p> Signup and view all the answers

    What is the function of histidine (H57) in the active site of chymotrypsin?

    <p>Proton acceptor</p> Signup and view all the answers

    Which class of proteases requires Ca++ as a cofactor and is found in Eukaryotes and Eubacteria, but not Archaea?

    <p>Calpains</p> Signup and view all the answers

    Which enzyme is known for cleaving precursor proteins and is a homodimer with one active site per subunit?

    <p>HIV Protease</p> Signup and view all the answers

    Which protease has an active site composed of the amino acids His-His-Glu and requires Zn as a cofactor?

    <p>Thermolysin</p> Signup and view all the answers

    In the liver, Alcohol Dehydrogenase (ADH) uses NAD+ to convert alcohols to which compound?

    <p>Acetaldehyde</p> Signup and view all the answers

    Which term best describes the relationship between enzymes and effectors?

    <p>Allosteric</p> Signup and view all the answers

    In enzyme diversity, how many biological reactions/enzyme categories are typically recognized?

    <p>Six</p> Signup and view all the answers

    Which enzyme is associated with the need for speed in enzyme catalysis?

    <p>Chymotrypsin</p> Signup and view all the answers

    What type of binding does hemoglobin demonstrate as a case study in enzyme diversity?

    <p>Cooperative binding</p> Signup and view all the answers

    In enzyme diversity, which term best describes the relationship between substrate binding and cooperativity?

    <p>Allosteric</p> Signup and view all the answers

    How many families of carbonic anhydrases have been discovered?

    <p>8</p> Signup and view all the answers

    What metal ion is used by the η family of carbonic anhydrases?

    <p>Zinc</p> Signup and view all the answers

    What catalytic strategy is employed by the active site of carbonic anhydrases?

    <p>Covalent catalysis</p> Signup and view all the answers

    What is the medical application of carbonic anhydrases related to artificial lungs?

    <p>Carbon dioxide removal</p> Signup and view all the answers

    How many splice variations of carbonic anhydrases are produced by humans?

    <p>15</p> Signup and view all the answers

    What is the role of an apoenzyme?

    <p>To form the whole active enzyme</p> Signup and view all the answers

    In the context of enzyme diversity, which type of reaction results in swapping functional groups?

    <p>Nucleophilic Substitution</p> Signup and view all the answers

    What is the preferred state of ATCase when CTP binds to it?

    <p>Tense (T) state</p> Signup and view all the answers

    What is the function of zymogens?

    <p>To require proteolytic activation</p> Signup and view all the answers

    What type of kinetics can multiple binding site enzymes follow if they are noncooperative?

    <p>Michaelis-Menten kinetics</p> Signup and view all the answers

    What is the role of effector binding in enzyme function?

    <p>To change the conformation of the enzyme</p> Signup and view all the answers

    What is the type of reaction catalyzed by serine proteases like chymotrypsin?

    <p>Hydrolysis reaction</p> Signup and view all the answers

    What is the catalytic triad of chymotrypsin composed of?

    <p>Cysteine, Histidine, Aspartate</p> Signup and view all the answers

    What is the main catalytic strategy employed by carbonic anhydrases?

    <p>Acid-base catalysis (Approximation)</p> Signup and view all the answers

    Why do we need proteases like chymotrypsin?

    <p>To synthesize shorter polypeptides</p> Signup and view all the answers

    What is the purpose of reversible covalent modifications in proteins?

    <p>To activate/inactivate the enzyme</p> Signup and view all the answers

    Which type of molecule is Myristic Acid?

    <p>A fatty acid</p> Signup and view all the answers

    What is the main contribution of carbohydrates to the proteome?

    <p>Adding diversity to the proteome</p> Signup and view all the answers

    Which color represents nucleotides in the structures referred to in the text?

    <p>Green</p> Signup and view all the answers

    What is the significance of ADP-ribose in reversible covalent modifications?

    <p>It is a common addition to nucleic acids</p> Signup and view all the answers

    What is the role of Farnesyl in reversible covalent modifications?

    <p>To serve as an intermediate in cholesterol synthesis</p> Signup and view all the answers

    What type of modification creates nonproteinogenic amino acids by adding functional groups to activate/inactivate enzymes?

    <p>Reversible covalent modifications</p> Signup and view all the answers

    What is the color used to represent fatty acids in the structures mentioned in the text?

    <p>Red</p> Signup and view all the answers

    In the context of enzyme diversity, what is the main difference between apoenzymes and holoenzymes?

    <p>Apoenzymes are inactive and lack cofactors, while holoenzymes are active and contain cofactors.</p> Signup and view all the answers

    When CTP binds to ATCase, what is the preferred state of the enzyme?

    <p>Tense (T) state</p> Signup and view all the answers

    What is the catalytic triad of chymotrypsin composed of?

    <p>Histidine, Serine, Aspartate</p> Signup and view all the answers

    What type of binding does hemoglobin demonstrate as a case study in enzyme diversity?

    <p>Homotropic allosteric binding</p> Signup and view all the answers

    What metal ion is used by the η family of carbonic anhydrases?

    <p>Zinc (Zn)</p> Signup and view all the answers

    What is the function of zymogens?

    <p>They are inactive and require proteolytic activation.</p> Signup and view all the answers

    What is the main contribution of carbohydrates to the proteome?

    <p>Stabilization of protein structures</p> Signup and view all the answers

    What is the main catalytic strategy employed by carbonic anhydrases?

    <p><strong>Nucleophilic addition</strong></p> Signup and view all the answers

    What is the function of the oxyanion hole in chymotrypsin's active site?

    <p>Stabilizes the tetrahedral intermediate (transition state)</p> Signup and view all the answers

    Which class of proteases requires Ca++ as a cofactor and is found in Eukaryotes and Eubacteria, but not Archaea?

    <p>Calpains</p> Signup and view all the answers

    What is the active site composition of the MMPs proteases?

    <p>His-His-Glu</p> Signup and view all the answers

    Which metal ion is required by Thermolysin's active site for its function?

    <p>Zn</p> Signup and view all the answers

    What is the role of Renin in the body?

    <p>Helps increase blood pressure and retain water/salt</p> Signup and view all the answers

    Which active site residues are split over a heterodimer by Calpains?

    <p>(S195) and (G193)</p> Signup and view all the answers

    What is the main role of Alcohol Dehydrogenase (ADH) in the liver?

    <p>Converts alcohols to acetaldehyde</p> Signup and view all the answers

    8.106

    <p>$NAD+$ resides in the active site of ADH</p> Signup and view all the answers

    What is the specific role of the S1 pocket in chymotrypsin's active site?

    <p>Determines placement of cut</p> Signup and view all the answers

    What is the main role of HIV Protease in cleaving precursor proteins?

    <p>Cleave precursor proteins</p> Signup and view all the answers

    What type of kinetics do Michaelis-Menten enzymes follow?

    <p>First order kinetics</p> Signup and view all the answers

    In the context of reversible reactions, at equilibrium, what is the condition that must be satisfied?

    <p>$k_1S = k_{-1}P$</p> Signup and view all the answers

    What are the two important equilibrium constants defined for reversible reactions?

    <p>Dissociation Constant and Association Constant</p> Signup and view all the answers

    What type of reaction does zero order kinetics represent?

    <p>Unimolecular reaction</p> Signup and view all the answers

    What kinetics does a reversible reaction follow at equilibrium?

    <p>$k_1S = k_{-1}P$</p> Signup and view all the answers

    What does the condition $k_1S = k_{-1}P$ signify in a reversible reaction?

    <p>The reaction is at equilibrium</p> Signup and view all the answers

    In Michaelis-Menten kinetics, what is true about catalysis?

    <p>It is a first-order reaction</p> Signup and view all the answers

    What type of reaction is indicated by the condition $k_1S = k_{-1}P$ in a reversible reaction?

    <p>$k_1S = k_{-1}P$ signifies that the reaction is at equilibrium</p> Signup and view all the answers

    Which type of kinetics do second-order reactions follow?

    <p>Bimolecular kinetics</p> Signup and view all the answers

    What is true about catalysis according to Michaelis-Menten kinetics?

    <p>It follows first-order kinetics.</p> Signup and view all the answers

    In which type of kinetics do Michaelis-Menten enzymes follow?

    <p>First order kinetics</p> Signup and view all the answers

    What is the interpretation of the condition $k_1S = k_{-1}P$ in a reversible reaction?

    <p>The substrate is being both used and created</p> Signup and view all the answers

    Which type of reaction does zero order kinetics represent?

    <p>Unimolecular reaction</p> Signup and view all the answers

    What is the main difference between Michaelis-Menten enzymes and first order kinetics?

    <p>Catalysis is not a first order reaction</p> Signup and view all the answers

    What type of kinetics can multiple binding site enzymes follow if they are noncooperative?

    <p>Michaelis-Menten kinetics</p> Signup and view all the answers

    In the context of Michaelis-Menten kinetics, what does the term 'Km' represent?

    <p>A dissociation constant for substrate binding</p> Signup and view all the answers

    What does the turnover number (kcat) in Michaelis-Menten kinetics indicate?

    <p>The number of substrate molecules converted per active site per time</p> Signup and view all the answers

    What does the equilibrium constant (KS) in Michaelis-Menten kinetics define?

    <p>The association constant for substrate binding</p> Signup and view all the answers

    How can the Michaelis-Menten model be simplified when not much product (P) is present and [E·P] is approximately 0?

    <p>By ignoring k-3 and k1</p> Signup and view all the answers

    What assumption allows the simplification of the Michaelis-Menten model to E + S ⇌ E·S → E + P?

    <p>Binding of the substrate is at equilibrium</p> Signup and view all the answers

    What is the Michaelis-Menten equation in its most familiar form?

    <p>$\frac{\nu_{max}}{\nu_0} = \frac{K_m + S}{S}$</p> Signup and view all the answers

    What does it signify if k2 is the rate-limiting step in the Michaelis-Menten kinetics?

    <p>$K_m \approx \frac{k_{-1}}{k_1}$</p> Signup and view all the answers

    What condition indicates that νmax is reached when the enzyme is fully saturated?

    <p>[E·S] = [E]T</p> Signup and view all the answers

    What does the abbreviation $\nu_0$ represent in the context of Michaelis-Menten kinetics?

    <p>Initial reaction rate</p> Signup and view all the answers

    What does the Michaelis constant ($K_m$) represent in Michaelis-Menten kinetics?

    <p>The concentration of enzyme-substrate complex at half of its maximum value</p> Signup and view all the answers

    What is the main difference between cooperative enzymes and noncooperative enzymes with respect to following Michaelis-Menten kinetics?

    <p>Noncooperative enzymes can follow Michaelis-Menten kinetics, while cooperative enzymes cannot.</p> Signup and view all the answers

    In the context of enzyme kinetics, what does the condition $k_1S = k_{-1}P$ signify in a reversible reaction?

    <p>The reaction is at equilibrium.</p> Signup and view all the answers

    Which catalytic strategy is commonly employed by enzymes according to Michaelis-Menten kinetics?

    <p>Acid-base catalysis</p> Signup and view all the answers

    What is the significance of the oxyanion hole in chymotrypsin's active site?

    <p>It stabilizes the transition state of the reaction.</p> Signup and view all the answers

    What type of enzyme kinetics do cooperative enzymes exhibit?

    <p>Sigmoidal kinetics</p> Signup and view all the answers

    In the context of Michaelis-Menten kinetics, what is the significance of the x-intercept in a Lineweaver-Burk plot?

    <p>It represents the reciprocal of the Michaelis constant (1/KM)</p> Signup and view all the answers

    How does the Hill coefficient (nH) differ in the context of cooperative binding as described by the Hill equation?

    <p>It is equal to 1 for non-cooperative binding and greater than 1 for cooperative binding</p> Signup and view all the answers

    What effect does a perfectly cooperative binder (n > 1) have on the approximation of θ in the Hill equation?

    <p>It leads to an overestimation of θ</p> Signup and view all the answers

    What does a Hill plot of Hemoglobin with nH > 1 indicate about its binding characteristics?

    <p>Positive cooperativity</p> Signup and view all the answers

    How does the slope of a Hill plot relate to the level of cooperativity in ligand binding?

    <p>The slope decreases with negative cooperativity and increases with positive cooperativity</p> Signup and view all the answers

    What is the relationship described by the Hill equation?

    <p>Binding analyses for multiple binding site enzymes</p> Signup and view all the answers

    In Michaelis-Menten kinetics, what does a poor enzyme with kcat > k-1 represent?

    <p>High catalytic efficiency</p> Signup and view all the answers

    What does the condition kcat/km = 1 indicate in the context of Michaelis-Menten kinetics?

    <p>Dominance of kcat over km</p> Signup and view all the answers

    What does the dissociation constant (KD) represent in terms of enzyme kinetics?

    <p>Affinity between enzyme and substrate</p> Signup and view all the answers

    What does the condition Km 𝜈0 = 𝜈max/2 indicate in Michaelis-Menten kinetics?

    <p>Half-maximal velocity of the reaction</p> Signup and view all the answers

    What is the reaction rate for an IRREVERSIBLE reaction?

    <p>ν = ΔS - ΔT</p> Signup and view all the answers

    Which representation of the reaction data is most suitable for determining the reaction order?

    <p>1/[S] vs. time</p> Signup and view all the answers

    What is the interpretation of the condition ν = k[S]n?

    <p>It indicates first-order kinetics</p> Signup and view all the answers

    What is the significance of the slope (k) in the linear response of 1/[S] vs. time?

    <p>It represents the rate constant (k)</p> Signup and view all the answers

    What does the term 'hyperbolic' refer to in kinetics trends?

    <p>A non-linear response in reaction rates</p> Signup and view all the answers

    In Michaelis-Menten kinetics, what does ν represent in the equation ν = νmax[S] / (Km + [S])?

    <p>Maximum reaction rate</p> Signup and view all the answers

    What does the value of Km indicate in Michaelis-Menten kinetics?

    <p>The concentration of substrate at half of Vmax</p> Signup and view all the answers

    Study Notes

    Enzyme Functions and Types

    • Ligases are responsible for forming chemical bonds by condensing two molecules with the hydrolysis of ATP.
    • Hydrolases break a chemical bond by adding water across it.

    Coenzymes and Vitamins

    • Thiamine (Vitamin B1) is a coenzyme that is a building block of Coenzyme A (CoA).
    • Coenzyme A is associated with fatty acid metabolism and the common theme is energy production.

    Enzyme Catalysis

    • Isomerases are responsible for rearranging the order of atoms in a molecule (isomerization).
    • Histidine (H57) is a key residue in the active site of chymotrypsin, a serine protease.

    Proteases

    • Calpains are a class of proteases that require Ca++ as a cofactor and are found in Eukaryotes and Eubacteria, but not Archaea.
    • Chymotrypsin is a serine protease that cleaves precursor proteins and is a homodimer with one active site per subunit.
    • Thermolysin is a metalloprotease that requires Zn as a cofactor.

    Enzyme Diversity

    • Enzyme diversity recognizes six biological reactions/enzyme categories.
    • Carbonic anhydrases are associated with the need for speed in enzyme catalysis.
    • Hemoglobin demonstrates cooperative binding, a case study in enzyme diversity.

    Carbonic Anhydrases

    • There are three families of carbonic anhydrases that have been discovered.
    • The η family of carbonic anhydrases uses Zn as a cofactor.
    • Carbonic anhydrases employ a catalytic strategy of metal-assisted acid-base catalysis.
    • Carbonic anhydrases have a medical application related to artificial lungs.
    • Humans produce 14 splice variations of carbonic anhydrases.

    Enzyme-Substrate Binding

    • Allosteric modulation occurs when an effector binds to an allosteric site, changing the enzyme's activity.
    • In noncooperative enzymes, substrate binding does not affect the enzyme's activity.
    • In cooperative enzymes, substrate binding affects the enzyme's activity, either positively or negatively.

    Protease Functions

    • Zymogens are inactive precursors of enzymes that are cleaved to form the active enzyme.
    • Chymotrypsin is a serine protease that catalyzes peptide bond hydrolysis.
    • The catalytic triad of chymotrypsin is composed of His-His-Glu.
    • The oxyanion hole in chymotrypsin's active site stabilizes the negative charge on the tetrahedral intermediate.

    Reversible Reactions and Kinetics

    • Michaelis-Menten kinetics describe the kinetics of reversible reactions.
    • In a reversible reaction, at equilibrium, the condition k1S = k-1P must be satisfied.
    • The condition k1S = k-1P signifies that the reaction has reached equilibrium.
    • Michaelis-Menten enzymes follow saturation kinetics.
    • The turnover number (kcat) in Michaelis-Menten kinetics indicates the enzyme's maximum catalytic rate.
    • The equilibrium constant (KS) in Michaelis-Menten kinetics defines the enzyme-substrate binding affinity.
    • The Michaelis constant (Km) represents the enzyme's substrate binding affinity.
    • Cooperative enzymes exhibit sigmoidal kinetics, while noncooperative enzymes follow Michaelis-Menten kinetics.

    Hill Equation and Cooperative Binding

    • The Hill equation describes cooperative binding in enzymes.
    • The Hill coefficient (nH) represents the level of cooperativity in ligand binding.
    • A Hill plot of Hemoglobin with nH > 1 indicates positive cooperativity in ligand binding.

    Enzyme Inhibition and Regulation

    • In reversible reactions, the dissociation constant (KD) represents the enzyme-inhibitor binding affinity.
    • In Michaelis-Menten kinetics, a poor enzyme has kcat > k-1, indicating slow product release.
    • The condition Km ν0 = νmax/2 indicates that the enzyme is operating at half-maximal velocity.
    • The reaction rate for an irreversible reaction is given by the equation ν = k[S]^n.

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    Enzymes: Catalysis, Kinetics, Binding PDF

    Description

    This quiz covers the topic of enzyme allosteric regulation, involving a second substrate which can act as an activator or inhibitor. It also discusses the role of ATCase in metabolism and the binding preferences of CTP and ATP for the T/inactive and R/active states.

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