The drug imatinib acts by inhibiting which of the following enzyme?

Imatinib is a tyrosine kinase inhibitor domain of BCR-ABL oncoprotein and prevents phosphorylation of the kinase substrate by ATP. It is indicated for the treatment of chronic myelogenous leukemia and gastrointestinal stromal tumors. 5 Fluorouracil inhibits thymidylate synthase thereby interfering with synthesis of DNA to lesser extent RNA. Its effect is more marked on atypical, rapidly proliferating cells. It is used topically for the treatment of multiple actinic keratoses. Ref: Chu E., Saorelli A.C. (2012). Chapter 54. Cancer Chemotherapy. In B.G. Katzung, S.B. Masters, A.J. Trevor (Eds), Basic & Clinical Pharmacology, 12e.