A door locking mechanism is contained within a cartridge for use with a tubular style door lock. The cartridge activates and deactivates the door lock with a manual depression of a push button. Depressing the push button causes a cam to rotate thus converting the axial motion of the push button into a rotary motion thereby activating the door lock. Once locked, both the interior and exterior door knobs may not be rotated. In order to unlock the door, the push button is depressed a second time thereby rotating the cam in an opposing direction and deactivating the door lock.