# DBT JRF 2022 — Question 30

Exam: DBT JRF 2022 · Section: A · Topic: Cell Biology › Signal Transduction - Phospholipase C Pathway · Difficulty: Medium

## Question

During signal transduction, one molecule of phosphatidylinositol 4,5-bisphosphate (PIP2) is cleaved into one molecule each of inositol triphosphate (IP3) and diacylglycerol (DAG) by the enzyme:

## Options

- **A.** Lipolyase C
- **B.** Phosphatase C
- **C.** Phosphodiesterase C
- **D.** Phospholipase C

## Answer

Option D

## Explanation

Phospholipase C (PLC) and PIP2 cleavage in signal transduction: In the IP3/DAG signalling pathway: 1. A ligand (e.g., hormone) binds its receptor → activates a G-protein (Gq) or RTK → activates Phospholipase C-β (or PLC-γ). 2. PLC cleaves PIP2 (phosphatidylinositol 4,5-bisphosphate) at the phosphodiester bond: $\text{PIP}_2 \xrightarrow{\text{PLC}} \text{IP}_3 + \text{DAG}$ 3. IP3 (inositol 1,4,5-trisphosphate): diffuses to the ER, opens IP3R Ca²⁺ channels → calcium release → activates calmodulin-dependent kinases. 4. DAG (diacylglycerol): stays in the membrane → activates Protein Kinase C (PKC) → phosphorylates downstream targets. The enzyme is Phospholipase C (not Lipolyase, Phosphatase, or Phosphodiesterase C — none of these are real enzyme names for this reaction). Answer: Phospholipase C (Option 4).

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