Phosphorylation of a protein or enzyme affects its activity most by inducing conformational change of this enzyme. Does anyone know if phosphorylation could affect Vmax and Km?
Hi Meiyue Wang,
If we analyse this concept theoretically, then we can speculate that if phosphorylation is affecting the enzyme catalytic activity by changing its structure, therefore the possibility of substrate binding to the enzyme (due to conformational change) will be affected and consequently it will lead to either reduced activity of an enzyme (Km would be higher, substrate binding is low) or it will inhibit the catalytic reaction which could ultimately affect Vmax of the reaction, As Vmax is related to "Kcat" of the reaction. So, Kcat would be affected as well.
Thank you,
Regards
Phosphorylation can definitely affect enzyme kinetics by inducing conformational changes or supplying an additional metal binding site etc. You can perhaps look up papers that describe enzyme's activity before and after phosphorylation (e.g. Article Activation Loop Phosphorylation Modulates Bruton's Tyrosine ...
).Good luck!
Yes it does, this study indicated, phosphorylation primary effect was that it increased the Km for each of the substrate proteins but no change was seen in Vmax in the reaction.
Effects of Phosphorylation of Protein Phosphatase 1 by pp60v-src on the Interaction of the Enzyme With Substrates and Inhibitor Proteins by J W Johansen et al.
Nature would not invest the energy to do a phosphorylation unless it has an important effect, such as activation, which is a change of kcat and/or KM. "Just" a conformational change without effect on activity (and maybe stability) would not make sense.
Kinases is an enzyme class doing phosphorylations to regulate the activity.
Thus the purpose of the phosphorylation-induced conformational change is to modify kcat and/or KM.
Phosphorylation of a protein is occurred by the addition of a covalently bound phosphate group. Together with its counterpart, dephosphorylation, it is critical for many cellular processes. Protein phosphorylation alters the structural conformation of a protein, causing it to become activated, deactivated, or modifying its function. For example, phosphorylation of the enzyme glycogen synthetase changes the enzyme’s shape and reduces its activity. Since Km is a measure of the affinity of the enzyme for its substrate, phosphorylation of an enzyme affects its ability to interact with its substrates .similarly Vmax will be affected.
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