Create Animation in unity3d only on one axis

Hi , i try to create animation in unity3D for move game object between -5 and 5 on x axis . i want to when i attach this animation to object it`s move between -5 and 5 , but my problem is : when i add curve to x axis unity automatically add curve to y and z too ! so when i attach this animation to other object it`s change object transform position on x y z axis but i only need to move on x ! what should i do for solve this problem ? thanks