This is a standard NAD⁺ dependent oxidation. It is initiated with a protein bound base (HIS in this case) pulling on the H of the hydroxyl group of the alcohol carbon. The pair of electrons from the O^- starts to swing towards the carbon. Simultaneouly the H^- (hydride) on the same carbon is transferred to NAD⁺ with the subsequent internal rearrangements.

The results of the previous step are shown. NADH and oxaloacetae are the products. Remember this is a freely reversible reaction and indeed the standard state thermodynamics substnatially favors malate formation

Aerobic Glucose Metabolism

Malate Dehydrogenase Information

Reaction

Rationale

Thermodynamics

Mechanism

Pictures

JMOL

Enzyme Name	Malate Dehydrogenase

Reaction Catalyzed	Redox
Reaction Type	Oxidation - Reduction
Pathway Involvement	Citric Acid Cycle
Cofactors/Cosubstrates	NAD⁺/NADH are the cosubstrate/coproduct

ΔG^o'	+29.7 kJ/M
	The Standard Free Energy favors moving the citric acid cycle in the "wrong" direction.
K_eq		Since this fraction is less than 1, then the concentrations of the substances on bottom (the substrates malate and NAD⁺) must be larger than those on the top WHEN the reaction comes to equilibrium.
Comments	Starting from standard state (all concentrations at 1 M/l) and allowing the reaction to come to equilibrium the substrates malate and NAD⁺ concentration would end up ~150,000 times higher than that of the products - oxaloacetate + NADH.
ΔG in a typical mitochondrion
	~0 kJ/M	Under typical conditions then, the forward and reverse observed rates of this reaction are about equal because the concentration of malate is very high relative to that of oxaloacetate.

Mechanism for Chemistry
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