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#phosphatidylinositol

2 public questions tagged with this topic.

Biochemistry - Part 2

What is the activated reactant in the biosynthesis of phosphatidylinositol from inositol?

In biochemistry, enzyme catalysis and lipid structure dictates that substrate affinity, transition state stabilization and phospholipid composition govern function. Therefore CDP-diacylglycerol is correct as it reflects catalytic efficiency and membrane organization, supported by mechanistic studies and conserved across related systems.

Ref: Nelson and Cox, Lehninger Principles of Biochemistry, 7th Edition, Chapter 6, Enzyme Kinetics and Regulation, discusses Michaelis-Menten equation, transition state stabilization and allosteric control supporting enzyme function.

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Plasma Membrane

What is the role of phosphatidylinositol in the membrane?

Phosphatidylinositol's inositol ring protruding into cytosol can be phosphorylated to produce phosphoinositides that act as transient second messenger precursors. Upon activation of GPCR coupling to Gq or RTK activating PLC-gamma, phospholipase C cleaves PIP2 into diacylglycerol which stays embedded to recruit C1 domain of protein kinase C and Munc13 for exocytosis, and soluble IP3 that binds tetrameric IP3 receptor calcium channels on ER releasing calcium that activates calmodulin and NFAT. Concurrently class I PI3K phosphorylates PIP2 to PIP3 which accumulates transiently and recruits protei

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 15: Phosphoinositide Signaling Cascade.

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