GHAP makes 1st high energy compound

Question 1

GAPDH, what kind of rxns, how is it saving ∆G ?

Answer 1

homotetramer that uses covalent catalysis in a redox reaction.

This rxn is essentially at equilibrium.
Oxidizing RCHO of GAP to form thioester.

This is saving the free energy (∆G) of the RCHO oxidation via synthesizing a thioester. In conjunction, you are reducing NAD+ to NADH.

Once thioester is formed, can synthesize an acyl-Phosphate which also saves ∆G.

1: from GAP to thiohemiacetal : Nuc addition to a carbonyl. NOT NAS, because youre forming from an RCHO which is not an acyl derivative.

Question 2

Step one

Answer 2

1: from GAP to thiohemiacetal : Nuc addition to a carbonyl. NOT NAS, because youre forming from an RCHO which is not an acyl derivative.

Question 3

step 2

Answer 3

Hydride transfer, even though Hydride is a bad leaving group, this is because they’re a really strong base. Creates thioester.

Question 4

step 3

Answer 4

NAS: FREE FLOATING phosphate attacks carbonyl of thioester.

Sulfur is acting as Nuc, e- sink and leaving group

Question 5

Hydride transfer rationale

Answer 5

Hydride addition is adding to the si face (counterclockwise).

Suggests that when adding to si face gets pro-s but only under certain contexts.

Overall energetics of the rxn allow use of the poor leaving group

Question 6

Where does hydride reduction/oxidation occur in G3PDH active site

Answer 6

C4 of NAD+

Question 7

which reactions in glycolysis occur twice

Answer 7

ATP rxns, 6,7,8,9,10 happen TWICE