Single Choice

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 ?

AMutation that increase the affinity of X for GDP.
BMutation that decrease the affinity of X for GDP.
CMutation that decrease the rate of GTP hydrolysis.
DMutation that prevent expression of enzyme X
Correct Answer

Solution

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.

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