peptidyl-prolyl cis-trans isomerase activity

Definition

Target type: molecularfunction

Catalysis of the reaction: peptidyl-proline (omega=180) = peptidyl-proline (omega=0). [EC:5.2.1.8]

Peptidyl-prolyl cis-trans isomerase (PPIase) activity is a crucial molecular function that plays a vital role in protein folding and function. PPIases catalyze the cis-trans isomerization of the peptide bond preceding proline residues. Proline, due to its cyclic structure, imposes constraints on protein folding by introducing a conformational rigidity. This makes the peptide bond preceding proline particularly slow to isomerize, often becoming a rate-limiting step in the folding process.

PPIases accelerate this isomerization reaction by lowering the activation energy barrier. They do this by binding to the peptide bond and facilitating the rotation around the peptide bond, thereby allowing the proline residue to switch between its cis and trans conformations. This isomerization is essential for achieving the correct three-dimensional structure of proteins.

The cis and trans conformations of the peptide bond preceding proline have significant impact on protein folding. The cis conformation often leads to a tight turn or loop structure, while the trans conformation allows for a more extended polypeptide chain. The correct isomerization state at each proline residue is crucial for proper protein folding, stability, and function.

PPIases are essential for various cellular processes, including:

* **Protein Folding:** They assist in the proper folding of newly synthesized proteins by facilitating the isomerization of proline residues.
* **Protein Maturation:** PPIases can contribute to the correct folding and assembly of multi-subunit protein complexes.
* **Signal Transduction:** Some PPIases are involved in regulating signaling pathways by modulating the activity of signaling proteins.
* **Cellular Stress Response:** PPIases can help in the refolding of misfolded or unfolded proteins under stress conditions, preventing protein aggregation.

PPIase activity is found in a wide range of organisms and is associated with different classes of enzymes, including cyclophilins, FK506-binding proteins, and parvulins. Each class exhibits distinct structural features and mechanisms, but they all share the ability to catalyze the isomerization of the peptide bond preceding proline residues.'
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Proteins (15)

Compounds (34)