activation of protein kinase A activity

Definition

Target type: biologicalprocess

Any process that initiates the activity of the inactive enzyme protein kinase A. [GOC:pde]

Protein kinase A (PKA) is a key enzyme involved in cellular signaling, regulating a wide range of biological processes. Its activation is a multi-step process initiated by the binding of cyclic AMP (cAMP) to the regulatory subunits (R) of the PKA holoenzyme. This binding event triggers a conformational change in the R subunits, leading to their dissociation from the catalytic subunits (C). The free catalytic subunits are now active and can phosphorylate specific target proteins, thus altering their activity. Here is a detailed breakdown of the process:

1. **Signal Reception:** The initial signal for PKA activation often originates from the binding of a ligand, such as a hormone, to a G protein-coupled receptor (GPCR) on the cell surface. This binding event initiates a signaling cascade that ultimately leads to the production of cAMP.

2. **cAMP Production:** The activated GPCR stimulates the activity of adenylyl cyclase, an enzyme responsible for catalyzing the conversion of ATP to cAMP. Increased levels of cAMP act as a second messenger, diffusing throughout the cell to activate PKA.

3. **Binding to Regulatory Subunits:** cAMP binds to specific sites on the regulatory subunits (R) of PKA, causing a conformational change in the R subunits. This conformational change weakens the interaction between the R subunits and the catalytic subunits (C).

4. **Dissociation of Subunits:** The binding of cAMP to the R subunits facilitates the dissociation of the R subunits from the C subunits. The free C subunits are now in their active form, ready to phosphorylate target proteins.

5. **Phosphorylation of Target Proteins:** The activated catalytic subunits of PKA can now phosphorylate specific serine or threonine residues on target proteins. This phosphorylation event can either activate or inhibit the activity of the target protein, depending on the specific protein involved.

6. **Signal Termination:** The signal for PKA activation is eventually terminated by the hydrolysis of cAMP to AMP by the enzyme phosphodiesterase. This decrease in cAMP levels allows the R subunits to re-associate with the C subunits, returning PKA to its inactive state.

The activation of PKA is a highly regulated process that ensures a precise and timely response to cellular signals. By controlling the phosphorylation of target proteins, PKA plays a critical role in a wide variety of cellular processes, including metabolism, cell growth, differentiation, and neurotransmission.'
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Proteins (1)

Compounds (3)