Q41E - Organic Chemistry (Mcmurry)

Question

One step in the gluconeogenesis pathway for the biosynthesis of glucose is the partial reduction of 3-phosphoglycerate to give glyceraldehyde 3-phosphate. The process occurs by phosphorylation with ATP to give 1,3-bisphosphoglycerate, reaction with a thiol group on the enzyme to give an enzyme-bound thioester, and reduction with NADH. Suggest mechanisms for all three reactions.
 

Step-by-Step Solution

Answer

The mechanism for the above conversion can be explained.

Step 1: Mechanism for phosphorylation of 3-phosphoglycerate

The carboxylate anion’s nucleophilic attack of 3-phosphoglycerate on P of ADP will yield intermediate. It again eliminates to give 1,3-bisphosphoglycerate.

Step 2: Mechanism for formation of enzyme bound thioester

The attraction of base from enzyme and the enzyme anion’s nucleophilic attack will takes place on 1,3-bisphosphoglycerate’s carbonyl carbon will give an intermediate. It again eliminates an ion of phosphate to give enzyme bound thioester.

Step 3: Mechanism for reduction of enzyme bound thioester with NADH

The NADH’s nucleophilic attack on carbonyl carbon of enzyme bound thioester will give an intermediate. It then eliminates the anion of enzyme bound thioester will give glyceraldehyde 3-phosphate.