Interconversions between the PPII and PPI helix forms of poly-proline are slow, due to the high activation energy of X-Pro cis-trans isomerization (Ea ≈ 20 kcal/mol); however, this interconversion may be catalyzed by specific isomerases known as prolyl isomerases or PPIases.
The change between the PPII and PPI helix forms of poly-proline is slow due to the high activation energy needed for X-Pro cis-trans isomerization (Ea ≈ 20 kcal/mol); however, this transformation can be catalyzed by prolyl isomerases or PPIases.