On the Mac the Option/Alt key is used to quickly enter non-ASCII characters. Komodo provides a few bindings involving control keys, like Alt+Return to edit a file's properties, but it stays away from the Alt/Option key for the most part.
I tried binding [Go to file...] to Cmd+Alt+K. The preferences dialog accepted it (although it said it was first bound to Cmd+¬, and later said it was bound to Cmd+Alt+Û, both of which gave me the feeling that the binding would fail to work. There have been Mozilla bugs dealing with inconsistencies in keybindings on OS X, and we're seeing that here.
Komodo will also let you create keybindings using combinations of the Command, Control, and Shift keys -- I would stick with those, and leave the Alt key for entering non-ASCII characters.