MadSci Network: Biochemistry

Re: Wh is the entrence of acetyl CoA in the kreb cycle a rate liimitingreaction

Date: Thu Jul 24 10:42:21 2008
Posted By: Karin Crowhurst, Assistant Professor, Biochemistry
Area of science: Biochemistry
ID: 1190519527.Bc

Hi Mark,

The mechanism of the citrate synthase-catalyzed reaction between oxaloacetate and acetyl-CoA is a multi-step mechanism (~3 steps). The first step of the mechanism, after which an enol intermediate is formed, is considered to be the rate-limiting step of the mechanism because there is a large energetic barrier between the reactants and the intermediate.

You may have been told that the deltaG for this reaction is a large negative number (about -32 kJ/mol), but just remember that deltaG is the difference between the free energy of the reactants and products of a reaction, and says nothing about the pathway to get there. This reaction has a BIG energetic payoff, but getting there involves traversing at least one large energy barrier.


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