Question

If there is an excess of ATP what are the enzymes and reactions that will be inhibited or decreased in Glycolysis and Gluconeogenesis and Glycogenolysis? (For example, An excess of ATP would inhibit PFK1.)

Answer 1

Ans-Most steps in gluconeogenesis are the reverse of those found in glycolysis, three regulated and strongly exergonic reactions are replaced with more kinetically favorable reactions. Thus the glycolytic enzymes pyruvate kinase, phosphofructokinase, and hexokinase/glucokinase are replaced with PEP carboxykinase, fructose-1,6-bisphosphatase and glucose-6-phosphatase. This system of reciprocal control where activation or inhibition of glycolysis is accompanied by the inhibition or activation of gluconeogenesis respectively avoids the formation of a futile cycle. The rate of gluconeogenesis is ultimately controlled by the action of the key enzyme, fructose-1,6-bisphosphatase, which is also regulated through signal transduction by cAMP and by phosphorylation. Most factors that regulate the activity of the gluconeogenesis pathway do so by inhibiting the activity or expression of key enzymes. However, both acetyl CoA and citrate activate gluconeogenesis enzymes (pyruvate carboxylase and fructose-1,6-bisphosphatase, respectively). Due to the reciprocal control of the cycle, acetyl-CoA and citrate also have inhibitory roles in the activity of pyruvate kinase