A biologist discovers a new signal transduction pathway in fruit flies that involves a protein kinase cascade.As part of a grant proposal he writes to obtain funding for further work on this pathway, the biologist proposes research to look for phosphatase enzymes.Why?
A) Since a signaling cascade contains multiple enzyme-catalyzed events, the biologist needs to identify all of the enzymes participating in the cascade.
B) Since a phosphatase enzyme catalyzes the removal of phosphate ion from a substrate, the biologist needs to be sure that none are interfering with the signaling cascade.
C) The biologist needs to identify the enzymes that provide the source of phosphate ions added to substrates during the signaling cascade.
D) The biologist needs to identify the enzymes that regulate the pathway by removing phosphate groups from molecules in the signaling cascade.
E) The biologist needs to identify all enzymes involved in phosphate ion transfer to determine whether they are involved in the pathway.

Question

Quizplus · Accepted Answer

The proposal is to look for phosphatase enzymes which remove phosphate groups from molecules. This implies that the biologist is looking for enzymes that regulate the pathway by deactivating the signaling cascade, as the removal of a phosphate group usually inactivates a protein. Therefore, Choice D is the best answer.

A Biologist Discovers a New Signal Transduction Pathway in Fruit