Transporter kinetics....distribution ratio vs. time

[SysBio]

Hello,

I have been looking through publications inorder to find the maximum rates of a few transporters...

 

this is easy when data is shown as V vs. S

you can just find Vmax from where the graph is leveling off

 

however, some data for transporters is shown as DISTRIBUTION RATIO vs TIME (where distribution ratio = inside cell / outside cell)

 

does anyone know:

1) why would someone display the data like this?...(ie. is it for transporters with very fast kinetics)?

2) how can you find Vmax for a transporter with this data?

[Mokele]

My guess is that it's for cells that are "leaky", like neurons are with potassium. They transport it one way, but it leaks back out/in.

 

As for determining Vmax, you could probably calculate it from the relative concentrations - once it levels off, you can calculate the rate stuff would leave a permeable membrane at that concentration, and the transporters must be equal to that if the concentration gradient is constant over time.

 

However, take this with a grain of salt - I'm a morphologist, not a molecular biologist.

 

Mokele