2. First reaction of kreb cycle, catalyzed by citrate synthase is inhibited by high level of NADH, ATP and succinyl-CoA.
3. Isocitrate dehyrogenase is inhibited by high level of ATP, NADH where as Ca²⁺ and ADP stimulate this step.
4. α-ketoglutarate dehydrogenase is inhibited by succinyl CoA and high level of NADH where as Ca²⁺ stimulate this step
In addition, rate of glycolysis indirectly regulates the kreb cycle through availability of pyruvate in the feeding step. To maintain good co-ordination between two metabolic pathways, citrate produced in first step of kreb cycle is an allosteric inhibitor of phosphofructokinase-1 in the glycolytic pathway.
Significance of Kreb Cycle:

1.  As a master regulator of metabolism- Kreb cycle is centrally connected to metabolic intermediates of carbohydrate, protein and lipid metabolism (Figure 37.3).  It has several branching points where it can communicate with either protein or lipid metabolism. Lipid metabolism is connected to kreb cycle through common intermediated as citrate and acetyl Co-A.