Isocitrate Dehydrogenase (IDH)

Question 1

structure of IDH

Answer 1

3 subunit types, assemble into heterotetramer and then into an octamer as well.
The two types: one use NAD+ and some that use NADP+ (not in TCA)

Question 2

importance of IDH

Answer 2

• key regulatory step, and first link with Ox-phos via the fuel being NADH

Question 3

stereospecificity

Answer 3

stereospecific hydride addition to NAD+, dont need to know the specific face in this case.

Question 4

CO2 lost from…

Answer 4

not from Pro-S or Pro-R arms…. coming from A prior acetyl-coA…

Question 5

something coming from Pro-S vs Pro-R arm

Answer 5

Pro-S = coming from current turn
Pro R = ??

Question 6

Intermediates

Answer 6

taken OH from specific arm of isocitrate, converted into a ketone… to create an e- sink to aid in the decarboxylation.
e- sink has additional help from Mn2+, but probably Mg2+ in vivo…. they are used to polarize the central C=O to make the
Point: divalent metal (Mg2+) will allow for a better pull on the carbonyl to make it a better e- sink…. similar to Zn in PC…
CO2 then leaves and left with decarboxy system

Question 7

How to remove enolate system to create keto system?

Answer 7

by adding a proton