We consider a five-dimensional nonlinear pde associated to the five-dimensional equation introduced by Martinez Alonso and Shabat. For our equation we and differential coverings with nonremovable parameters and list its reductions to known 4D and 3D integrable equations. One of the coverings produces a new family of integrable 5D equations. We show that each pair of these equations is related by a Backlund transformation, including the Backlund autotransformation for each equation from the family. Also we find a recursion operator for symmetries of the equation and study its action.