The T form of the enzyme must be stabilized by the protonated form of an amino acid side chain whose pKa is in the neighborhood of 7. Assume that the metabolic pathway shown below is operating at steady state in a cell. The numbers above the arrows are the rates of the forward reactions only. Assuming that the mechanism of control involves allostery, use the axes below to show how you would expect the regulatory enzyme to be affected by the allosteric effector. Be sure to label the horizontal axis.
P is likely to be a negative allosteric effector.
The one in the presence of P is to the right of the one in the absence of P. f. Propose an alternative regulatory mechanism, that does not involve allostery. High concentrations of tyrosine activate a protein kinase that phosphorylates, and thus inactivates, the enzyme. Assume that each catalytically active enzyme in the regulatory cascade from glucagon to glycogen phosphorylase has a turnover number of 1000 per second. Assume further that 10 activated G proteins are formed for each molecule of glucagon bound to the receptor. The binding of one molecule of glucagon to its receptor would generate 10 activated G-proteins.