gconftool-2 as root

Hi everybody,

I'm trying to change users proxy settings from root account, with the follo=
wing
command

su jose -c "gconftool-2 --type string --set /system/http_proxy/host
someproxy.com"

However, the command does nothing. If I login with my user, then "su" to the
root account, and then execute the previous command, it works.

So I suppose that it is something related to login, like environment variab=
les.
However, the "su --login" command doesn't help.

Anyone knows why it is not possible to change user's gconf with gconftool-2
logged in as root?

I'm using Debian Wheezy

Thanks!
Jos=E9.