Correct option is A
PI3-Kinase (phosphoinositide 3-kinase) phosphorylates the inositol ring of PI(4,5)P₂ at the 3′ position to generate PI(3,4,5)P₃. This conversion is a key step in intracellular signaling pathways, such as those involving growth factor receptors. PI(3,4,5)P₃ acts as a second messenger, recruiting proteins with pleckstrin homology (PH) domains, such as Protein Kinase B (PKB/Akt), to the membrane, where they participate in downstream signaling.
Information Booster:
- PI3-Kinase plays a central role in growth, survival, and metabolism signaling pathways.
- PI(4,5)P₂ is a precursor for both PI(3,4,5)P₃ and diacylglycerol (DAG).
- PTEN reverses this reaction by dephosphorylating PI(3,4,5)P₃ to PI(4,5)P₂.
- PLCβ hydrolyzes PI(4,5)P₂ to generate DAG and IP₃.
- PI(3,4,5)P₃ facilitates membrane recruitment and activation of signaling proteins.
Additional Knowledge:
- PI3-Kinase (Option a):
This enzyme phosphorylates PI(4,5)P₂ at the 3′ position, producing PI(3,4,5)P₃. It plays a critical role in pathways activated by receptor tyrosine kinases (RTKs) and G-protein coupled receptors (GPCRs). - PLCβ (Option b):
Phospholipase C beta (PLCβ) hydrolyzes PI(4,5)P₂ into DAG and inositol trisphosphate (IP₃). DAG activates protein kinase C, while IP₃ triggers calcium release from the endoplasmic reticulum. - PTEN (Option c):
PTEN is a phosphatase that dephosphorylates PI(3,4,5)P₃ at the 3′ position, converting it back to PI(4,5)P₂. It acts as a tumor suppressor by counteracting PI3-Kinase activity. - Protein Kinase B (Option d):
Also known as Akt, Protein Kinase B is not an enzyme that acts on PI lipids. Instead, it is activated downstream of PI3-Kinase by binding to PI(3,4,5)P₃ at the membrane.
