A 58-year-old man with chronic myeloid leukemia (CML) is started on imatinib, a drug that inhibits BCR-ABL tyrosine kinase, preventing uncontrolled cell proliferation. The oncologist explains that phosphorylation is a reversible modification used for rapid enzyme regulation, and many cancer treatments target enzymes involved in phosphorylation pathways. Which of the following best describes a reversible covalent modification involved in enzyme regulation?
