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Allosteric Enzyme Conformations definitions

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  • Allosteric Enzyme
    Protein with multiple conformations, each displaying distinct catalytic activity and substrate affinity, often regulated by effectors.
  • Conformation
    Three-dimensional structural state of a protein, determining its functional properties and substrate binding efficiency.
  • T State
    Catalytically inactive form with low substrate affinity, favored at low substrate concentrations and represented by a tense structure.
  • R State
    Catalytically active form with high substrate affinity, characterized by a relaxed structure and efficient substrate binding.
  • Active Site
    Region within an enzyme where substrate molecules fit and undergo chemical transformation, its accessibility varies by conformation.
  • Allosteric Constant
    Ratio of the concentration of tense states to free relaxed states in absence of substrate, indicating equilibrium preference.
  • Sigmoidal Kinetics
    S-shaped curve on enzyme activity plots, reflecting cooperative substrate binding and deviation from Michaelis-Menten behavior.
  • Positive Cooperativity
    Phenomenon where binding of one substrate molecule enhances the likelihood of additional substrate molecules binding.
  • Michaelis-Menten Kinetics
    Enzyme activity pattern showing a rectangular hyperbola, typical for non-cooperative enzymes with a single active site.
  • Concerted Model
    Theory proposing all subunits of an enzyme switch conformations simultaneously, explaining cooperative binding and sigmoidal kinetics.
  • Sequential Model
    Theory suggesting subunits change conformation individually upon substrate binding, allowing for intermediate states and cooperativity.
  • Allosteric Effector
    Molecule that binds to an enzyme at a site other than the active site, modulating its activity and conformation.
  • Subunit
    Individual protein component within a multi-unit enzyme, each capable of adopting different conformations and contributing to overall function.
  • Enzyme-Substrate Complex
    Association formed when substrate binds to the enzyme's active site, often representing the catalytically active relaxed state.
  • Le Chatelier's Principle
    Concept describing how equilibrium shifts to counteract changes, such as substrate binding altering enzyme state distributions.