Malate-Aspertate Shuttle + G3P

What problem do the shuttles solve?

Cytosolic NADH can't cross the inner mitochondrial membrane, so the shuttles carry its electrons in instead.

Where is the malate-aspartate shuttle used?

Liver, heart, kidney.
Mnemonic: "Malate for the Major organs."

Step 1 in the cytosol?

OAA + NADH → malate + NAD⁺ (MDH1).

How does malate get into the matrix?

Malate-α-KG antiporter (malate in, α-KG out).

What happens in the matrix?

Malate + NAD⁺ → OAA + NADH (MDH2). This NADH feeds Complex I.

Why must OAA be converted to aspartate?

OAA can't cross back out. Glutamate gives it an amino group → aspartate + α-KG (AST/GOT2, B6).

How does aspartate leave?

Glutamate-aspartate antiporter (aspartate out, glutamate in), driven by the proton gradient.

How is OAA regenerated in the cytosol?

Aspartate + α-KG → OAA + glutamate (AST/GOT1, B6).

ATP yield?

2.5 per cytosolic ATP