What does this statement mean - The uptake of substrate at a specific concentration may reflect both Km or Vmax or both. If Km of a transporter is independent of one of its regulator then the difference in the absence or presence of this regulator reflects its effect on Vmax.
As I understand the question, one typically wishes substrate to be in excess to make a reaction independent of substrate concentration. With a large substrate excess, the amount of free substrate ~equals the initial substrate so back reaction complications can be ignored.
@ Trainer: But the statement actually states that the concentration of substrate is such that it can affect Km, Vmax or both, indicating that it is in the linear phase and not at the saturating point.
What I did not understand is the second part - If Km of a transporter is independent of one of its regulator, then shouldn't the difference in the absence of this regulator reflect any of the changes - that is Vmax or Km or both?
If Km of a transporter is independent of one of its regulators, then the absence of this regulator cannot by definition alter Km so it presumably impacts Vmax.
@ Tainer: If Km of a transporter is independent of one of its regulator, then, wont it be the presence of this regulator that should impact the Vmax?
I think either the presence or absence of this regulator could impact the Vmax as it could be a negative or positive regulator.
In that case, If there is one regulator which is independent of the Km and during its absence another transporter which affects the Km is added, then will it mean that in the absence of the first regulator, the effect seen in the presence of the second regulator is now a Km effect?
A positive or negative regulator may impact Vmax by for example moving residues into a more effective transport position or impacts release on the other side of the membrane without altering the binding affinity Km per se.
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