Question

Enzymes X catalyzes hydrolysis of GTP into GDP. The GTP-bon from of Z transmits a signal that leads to cell proliferation. The GDP-bound from does not transmit any such signal. Mutations in X are in many cancers. Which of the following alterations of X are most likely to contribute to cancer ?

• A. Mutation that increase the affinity of X for GDP.
• B. Mutation that decrease the affinity of X for GDP.
• C. Mutation that decrease the rate of GTP hydrolysis.
• D. Mutation that prevent expression of enzyme X

Answer 1

Answer: (D)

Mutation that prevent expression of enzyme X

GTP-bound from Z are regulated by enzymes X , which results in the regulation of cell proliferation. Without enzymes X or any mutations in X , it is unable to hydrolysis GTP-Z or hydrolysis less GTP-Z. Enzyme X cannot activate a nonfunctional enzyme, and the Z protein is constitutively active, it leads to unregulated cell proliferation and the formation of tumors. Thus, the correct answer is option D.