Regulation of Krebs cycle

The regulatory points (enzymes) of the Krebs cycle are:

1. Citrate synthase
2. Isocitrate dehydrogenase
3. α-ketoglutarate dehydrogenase

Krebs cycle

The regulatory factors of the Krebs cycle are:

1. NADH / NAD⁺ ratio – respiratory control
2. ATP / (ADP a AMP) ratio – energy control
3. Krebs cycle substrate availability - substrate control

NADH / NAD⁺ ratio – respiratory control

The continuation of the Krebs cycle is the respiratory chain, where reduced cofactors are reoxidized. If NADH + H + and FADH₂ accumulate (NADH / NAD + ratio increases ), α-ketoglutarate dehydrogenase and isocitrate dehydrogenase are inhibited.

ATP / (ADP a AMP) ratio – energy control

If there is enough energy, α-ketoglutarate dehydrogenase and isocitrate dehydrogenase are inhibited.

• ATP is their inhibitor.
• ADP and AMP, on the other hand, are activators.

Krebs cycle substrate availability - substrate control

Substrate control is found at the level of citrate synthase, which produces as much citrate as we supply it with oxaloacetate and acetyl-CoA .

Krebs cycle activity is also related to O₂ availability. Even though none of the reactions in the cycle require O₂ , oxygen is needed for the respiratory chain because it serves as the final electron acceptor. In the respiratory chain, the following are reoxidized:

NADH → NAD⁺

FADH₂ → FAD

If the cell lacks O₂ , the concentration of NAD⁺ and FAD decreases, and subsequently the activity of the Krebs cycle also decreases.

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