I would like to understand if there is a relationship between the optimum pH of the enzyme activity and the pI. I don't have a clear-cut idea about why it should be like that. Please help.
Dyoni, I think there are not relationship between these two properties. Can you be more specific in your question? The optimum pH depends on the amino acid components of active site. The Isoelectric point depends of the full enzyme primary and tertiary structure. Particularly I've never seen a relationship between these two properties.
Hi there! I agree with what Zaira says. By definition the pI is the pH at which your protein carries no NET charge and that depends of the pKa of each protonable residue in the native structure. If some residues have non-canonical pKa values that certainly will change the pI, of course this could change in intermediate states, but this is not the case. I don't see a clear relationship between these two properties.
The pI and pH optimum are not related. To put it simply, at the pH optimum, the pH is such that, some amino acids groups are positively charged, and some are negatively charged, so that the substrate can bind to the active site through electrostatic interactions. More importantly, at the pH optimum, the charges (positive or negative) on certain amino acids (catalytic residues) are critical, for the actual enzymatic reaction or catalysis to take place.
Thanks for your answers Zaira, Diego and Stephanie,
I wasn't specific in my question. I'm working with carbohydrate esterases, and in a first plot analysis pI against pH, I found a low correlation between these properties.
Dear Zaira, Diego, and Stephanie.
So, is it possible that optimum pH is near (or same) to pI value? Or it is the opposite? Please give me your opinion. Thank you
As others have previously stated, there is no correlation between the pI of an enzyme and the optimal pH for its activity. The two values could be the same by coincidence.
Hi Susi, now I agree with Adam
pI and pH could be the same values and did not present correlations.
I understand now, the value is same but no correlation. Thank you Adam and Dyoni.
I am not sure they are unrelated. At isoelectric point, enzymes precipitate and the interaction between enzyme and substrate could be compromised. Active site charges are important for interaction with substrate; so I think there must exist a negative effect between pH and optimal enzymatic activity.
- Badges
- Science topic
- Similar topics
- Correction