[Nescafe]

Hi,

What does the apparent mean, where does it come from? Lets say this is in the context of Michaelis Menten kinetics.

Thanks,

Nescafe.

[Babcock_Hall]

There may be two separate questions here.  One, the Michaelis constant K_m is sometimes approximately equal to the dissociation constant of the substrate, but it can be less than, equal to, or greater than the dissociation constant in general.  Two, I sometimes use the word "apparent" to mean only for a certain, specified set of conditions.  Let us take creatine kinase as an example.  It has two substrates, creatine and MgATP.  Suppose that I fix the MgATP concentration at a value that is not saturating and vary the [creatine].  I would find the [creatine] that produces a velocity equal to V_max/2, and I would call this the apparent K_m of creatine.  The true K_m of creatine only refers to the situation in which all other substrates are saturating.  Borek may be a good person to ask about things like apparent pK_a values.

[Nescafe]

There may be two separate questions here.  One, the Michaelis constant K_m is sometimes approximately equal to the dissociation constant of the substrate, but it can be less than, equal to, or greater than the dissociation constant in general.  Two, I sometimes use the word "apparent" to mean only for a certain, specified set of conditions.  Let us take creatine kinase as an example.  It has two substrates, creatine and MgATP.  Suppose that I fix the MgATP concentration at a value that is not saturating and vary the [creatine].  I would find the [creatine] that produces a velocity equal to V_max/2, and I would call this the apparent K_m of creatine.  The true K_m of creatine only refers to the situation in which all other substrates are saturating.  Borek may be a good person to ask about things like apparent pK_a values.

That is all I needed thank you very much!