Question

1. Provide a mechanistic explanation for how intramuscular energy status can directly impact the rate of glycogenolysis, glycolysis, and TCA cycle activity during exercise. Hint: consider the allosteric regulation of specific enzymes.

Answer 1

Allosteric regulation refers to binding of substrate to the enzyme other and its active site and regulating the activity. High levels of ATP allosterically inhibit the enzyme, thus by lowering the affinity for fructose 6 phosphate. Thus hyperbolic binding curve is converted to sigmoid curve. Th increase in AMP can reverse the effect. ATP is generated by degradation of glucose, that is during excercise.

In muscle glycogen phosphorylase exists in two forms as GPa and GPb form. Glucogen 6 phsphate is released by glycogen breakdown, it is not normally found in the muscle.

Mostly GPa favors 'R ' state and GPb favours T' state. Conversion between T and R state involves allosteric interactions. When ATP bind to the GPb T state is favoured. and When AMP binds R state is favoured. During excercise most of the GPb will be in inactive form.