What my FCOM says about ALPHA PROT SPEED:
FCOM DSC-31-40 AIRSPEED
...corresponding to the angle of attack at which alpha protection becomes active (displayed when in Pitch normal law)
FCOM DSC 27-20-10 PITCH CONTROL - PROTECTIONS
Va Prot, Va Floor, Va Max vary according the weight and configuration
Below 200ft the AOA is also deactivated
http://www.a320quiz.com