Changing the email address of a key

[Richard Ulrich]

When I generated my new private key, I used one of my email addresses.
This email address is stored both on the crypto stick (smart card) and
in the secring.gpg or pubring.gpg, probably both.
Now I would like to use that key with another email address. 
Is it possible to change the email address of a key, and how would I
proceed to have it on the stick and in the gpg stub files?

Rgds
Richard