Question

Pyruvate dehydrogenase is _______________ when the ratio of atp to adp (atp/adp) are high.

Answer 1

Inactive

Step-by-step explanation:

Pyruvate dehydrogenase controls the production of acetyl CoA. This conversion is regulated by regulators like ADP, ATP, AMP and NADH. While ADP and AMP are regulators that enhances the activity of the Pyruvate dehydrogenase enzyme, regulators like ATP and NADH reduces the activity of the Pyruvate dehydrogenase enzyme. Thus, when the ratio of ATP to ADP is high then the inhibitory regulator i.e ATP is in large amount than the ADP. Hence, ATP reduces the activity of enzyme Pyruvate dehydrogenase and makes it inactive.

Answer 2

Pyruvate dehydrogenase is inactive when the ratio (ATP/ADP) are high. Phosphorylation of PDH is mediated by a special regulatory eznyme, pyruvate dehydrogenase kinase. This enzyme is part of the PDH multienzyme complex. Phosphorylation inactivates pyruvate dehydrogenase. The kinase is, in turn, subject to allosteric activation by NADH and acetyl-CoA, while it is inhibited by ADP, NAD+ and by free coenzyme A. When the ratio of ATP/ADP increases, pyruvate dehydrogenase kinase is activated which then inactivates PDH.