regarding comp inhibitors and km, Vmax - mlegriller

[ArchivalUser]

take the example of DHF and methotrexate

methotrexate acts on DHF reductase by competitive inhibition.
Q. if patients treated with methotrexate are given additional folate,
a)will the Vmax come back to what it was before methotrexate was given ?
b) DHF will have a higher apparent Km for dihydrofolate?

the answer is a but I have doubts regarding this because I thought that competitive inhibition does not change Vmax but only increases Km!
This is question no 41, biochem test 1 in Kaplan Q book.2005
Somebody please explain?

[ArchivalUser]

Vmax does not change with competitive inhibition means what is given in answer a) that Vmax will be same as it was before methotrexate was given. ITs just wordings I think causing little problem.

[ArchivalUser]

thanks smsin,

it is a matter of wordings, i think. since they say it comes back to previous Vmax, it means that the Vmax had changed with methotrexate (while my impression is that Km changes)

Can you clear this?