Question

PI 3-kinase acts by phosphorylating what molecule(s)?Choose one:

A. serines or threonines on protein kinases that phosphorylate Akt
B. tyrosines on protein kinases that phosphorylate Akt
C. inositol phospholipids
D. tyrosines of Akt
E. serines or threonines of Akt

Answer 1

PI 3-kinase phosphorylates inositol phospholipids, which act as secondary messengers in signaling pathways, leading to the activation of other kinases, including Akt.

Step-by-step explanation:

PI 3-kinase (Phosphoinositide 3-kinases) acts by phosphorylating inositol phospholipids. This action is distinct from that of protein kinase A (PKA) and protein kinase C (PKC), which phosphorylate proteinson their serine and threonine residues. Unlike PKA and PKC, PI 3-kinase is involved in signal transduction pathways that lead to the activation of other kinases like Akt (also known as protein kinase B), but it does this by generating second messengers through the phosphorylation of inositol lipids. PI 3-kinase specifically phosphorylates the 3' hydroxyl group of the inositol ring of phosphatidylinositol (PI), producing PIP (phosphatidylinositol phosphate), PIP2 (phosphatidylinositol bisphosphate), and PIP3 (phosphatidylinositol trisphosphate), which act as secondary messengers to continue the signaling cascade.