I. The gram negative bacteria Pseudomonas fluorescens oxidizes glucose by a pathway different from glycolysis in its initial steps. A key intermediate in this pathway is 2-keto-3-deoxy-6-Phosphogluconate (KDPG) which is cleaved by KDPG aldolase in a reaction analogous to that of fructose 1,6-diphosphate aldolase in glycolysis. The products of this reaction are metabolized by reactions familiar to you. The structure of KDPG is given below.

a. What are the products (D and E) of the KDPG-aldolase reaction? How are they formed mechanistically?

b. What amino acid is likely to be at the active site of KDPG-aldolase? How could this residue be labeled specifically?

c. If l-¹⁴C-glucose forms carboxyl-labeled KDPG, where would the label appear in the end products of fermentation, ethanol and CO₂? Compare this pattern to the glycolytic fermentation of l-¹⁴C -glucose.

d. One ATP is used up in the formation of KDPG from glucose. How many net ATPs are generated in the conversion of glucose to ethanol and CO₂ by this pathway? Compare this to glycolysis. Which is more efficient?

e. Make an intelligent guess at the intermediates A, B, and C between glucose and KDPG. Indicate the coenzymes, if any, involved in these reactions.

II.  The process of glucogenesis from pyruvate in liver does not involve the net incorporation of HCO₃^-; however, when liver tissue is incubated with pyruvate and H¹⁴CO₃^-, the glucose formed is radioactive.  Explain this result given that carbons 3 and 4 of glucose are labeled.  What carbons of glucose would be labeled starting with 3-¹⁴C-pyruvate?