PEPCK, GNG and metabolite transfer

Question 1

Liver

Answer 1

Has both PEPCK isozymes
Cytosolic (PEPCK1) and mitochondrial (PEPCK2).

Mito form is very active

Question 2

OA is always made where

Answer 2

in the mitochondria of liver

Question 3

Rest of GNG is where

Answer 3

in the cytosol.

Question 4

Why is it a problem that GNG occurs in the cytosol

Answer 4

need OA, which is from the mitochondria, and dont have a transporter to get OA out to the cytosol

How is it done then?
Use mitochondrial MDH to use OA to make malate, and use malate transporter to ship it out.
Then use cytosolic MDH to convert it back to OA

Question 5

Why are both of these processes occuring in the liver

Answer 5

Liver can do many metabolic rxns, so need a way to get those metabolic rxns completed, so will do either pathway to get it done.

Question 6

Why are NADH moved out indirectly

Answer 6

use mito NADH to make malate, use cytosolic NAD+ to make OA…. these NADH equivalents are used by GAPDH in glycolysis (bc occurs in cytosol)…

If start with lactate, dont need pathway to make NADH becayse LDH can be run backward