BIOL 541 1st Edition Lecture 9 Outline of Last Lecture I. Catalysis Outline of Current Lecture I. AllosterismII. MWC modelII. Koshland’s Induced fitIV. Co- enzymeCurrent LectureBiochem Lecture 9: Allosterism:Allosterism: Enzyme regulation is the ability of the substance (substrate or independent regulatory substance) to bind enzyme and alter affinity of enzyme for substrate, on either enzyme or subunit. Example: Positive cooperativity of hemoglobin where oxygen (substrate) on one alters other subunit. BPG to Hb- regulatory molecule attached to site changes Hb by changing velocity or affinity in terms of kinetic description.MWC (concerted) model: This model envisions that protein has 2 conformations- relaxed ® and tense (T) conformation. Equilibrium constant, L, is a lot higher for (T) and is favored. ® has higher affinity. Hence, in the absence of substrate, low affinity molecule persists: Hb is in deoxygenated state. Ligand perforated ® even in low concentration, or high affinity. Near equilibrium the reaction is driven by removal of the product to shift the equation in favor of forward direction.Disadvantage:These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.1. Descriptive but does not tell about the molecular level process.2. Further, does not explain negative cooperativity.Koshland’s induced fit (sequential model): When the substrate binds to the enzyme, it induces changes in conformation by either decreasing or increasing affinity or increasing or decreasing speed of reaction. This model covers all bases and is well grounded in molecular structures. The kinetic description is given by Hill’s co-efficient whereby when Hb is not fully cooperative, enzyme binds to multiple substrates. Therefore assume high cooperative and increase affinity where all oxygen is bound and no intermediates. If no cooperativity, then enzyme is a monomer (pure enzyme). When (slope) m=1 no cooperativity as in myoglobulin. Isocitrate dehydrogenase is highly cooperative tetramer with n=4. Hb is also a tetramer but n=2.8 because it is not fully cooperative or partially cooperative, therefore less than subunits m=2.8: Also, m less than 1 for negative coopeerativity. Co-factor: Is an non organic compound required for enzymatic activity. It is a metal ion example carboxy peptidase A for amine sequencing has Zn ion.Coenzyme: Is a non- proteinaceous organic compound required for enzymatic activity. For example, vitamins (not synthesized) in body are vital. Further as enzymes are catalytic in nature, less amount of vitamins are needed. Co- enzymes can be free in solution and picked up by enzymes. Some enzyme binds covalently to coenzymes. This strong binding creates prosthetic group (co-