TERMIUM Plus^®

Fiche 1,  Justifications,  Anglais

Record number: 1, Textual support number: 1 DEF

Plot that shows the pH activity relationship for a particular enzyme. Most enzymes have a characteristic pH at which their activity is maximal; above or below this pH the activity declines. Although the profiles of many enzymes are bell-shaped, they may vary considerably in form. Bell-shaped profiles with neutral substrates have often been interpreted as evidence that two ionizing groups of the enzyme are important in the catalytic reaction.  2, fiche 1, Anglais, - pH%2Dactivity%20profile

Record number: 1, Textual support number: 1 CONT

The previous discussion would suggest that all perturbations in the pH profile are characterized by a broadening or displacement of the profile towards acid or alkaline values. However pH profiles have been observed where both limbs are broadened, thus the effective rate of the enzyme becomes less sensitive to pH changes when it is immobilized. Such an effect can occur when neither proton partitioning nor diffusion limitation is present and is due to substrate diffusion limitation. An immobilized enzyme preparation that has a high enzyme loading (that is a large quantity of enzyme activity per unit of polymer) may be subject to substrate diffusion limitation.  3, fiche 1, Anglais, - pH%2Dactivity%20profile

Fiche 1,  Justifications,  Français

Record number: 1, Textual support number: 1 CONT

Le «protein engineering» est encore à ses débuts et on peut le comparer à ce qu'était le génie génétique en 1976. Il existe actuellement au moins quatre démonstrations, qui confirment que le concept est viable. [...] Un exemple est le travail effectué [...] sur la subtilisine. Sur une position du site de combinaison avec le substrat, ils effectuèrent les substitutions par les vingt mutants, l'un avait un profil de pH très particulier et des différences furent observées dans les spécificités des substrats de l'enzyme.  1, fiche 1, Français, - profil%20de%20pH

Fiche 1,  Justifications,  Espagnol