Chapter 19, Problem 3P

Assessing the Effect of Active-Site Phosphorylation on Enzyme Activity (Integrates with Chapter 15.) The serine residue of isocitrate dehydroenase that is phosphorylated by protein kinase lies within the active site of the enzyme. This situation contrasts with most other examples of coa1ent modification by protein phosphorylation. where the phosphorylation occurs at a sate remote from the active site. What direct effect do you think such active-site phosphorylation might have on the catalytic activity of isocitrate dehydrogcn.ise? (Sec Barford, D., 1991. Molecular mechanisms for the control of enzymic activity by protein phosphorytation. Biochimica et Biophysica Acta 1133:55—62.)