Accumulation of NADH inhibits the Krebs cycle by inhibiting:

Explanation

Accumulation of NADH inhibits the Krebs cycle primarily by suppressing enzymes involved in oxidative reactions. High levels of NADH indicate that the cell has enough reducing power, signalling a reduced need for further oxidation of metabolites. This leads to inhibition of key enzymes such as pyruvate dehydrogenase, which prevents the conversion of pyruvate into acetyl-CoA and slows the entry of carbon into the Krebs cycle. Within the cycle itself, NADH inhibits isocitrate dehydrogenase and α-ketoglutarate dehydrogenase, both of which are responsible for generating NADH during the oxidation of intermediates. By inhibiting these enzymes, the cycle's rate decreases, preventing overproduction of NADH and maintaining energy balance in the cell.