7.05 Problem Set 6 Spring 2008 TCA Cycle 1. α-Ketoglutarate plays a central role in the biosynthesis of several amino acids. Write a sequence of enzymatic reactions that could result in the net synthesis of α-ketoglutarate from pyruvate. Your proposed sequence must not involve the net consumption of other TCA cycle intermediates. Also, write an equation for the overall reaction with all reactants and products. (Exam 3, 2006) 2. In the presence of O 2 and malonate (at a high concentration) liver tissue was observed to metabolize malate. What would the end products be, and how much of each would be formed? Give the enzymatic reactions and show the reaction pathway. How many ATPs could be generated per malate metabolized? No need to give formulas. (Exam 3, 2005) 3. Give the mechanisms involved in the enzymatic conversion of α-ketoglutarate to succinyl-CoA. Please use structural formulas and indicate clearly the chemical mechanism of each proposed step. Use only coenzymes that have been discussed in class and enzymes of the type
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