Abstract: The present invention features a system and method for operating or operably connecting an American locking cylinder with a Profile mortise lock, wherein the American locking cylinder functions with the Profile mortise lock in place of a Profile locking cylinder. Essentially, the present invention provides a door lock cylinder conversion adapter that converts an American cylinder to be operable with a Profile mortise lock. The door lock cylinder conversion adapter functions to actuate the internal locking mechanism of a Profile mortise lock much the same way a standard Profile locking cylinder would, only with an American locking cylinder providing the means for effectuating the actuation.