AdS2-CFT1 correspondence leads to a prescription for computing the degeneracy of a single centered extremal black hole in terms of path integral over string fields living on the near horizon geometry of the extremal black hole. This prescription is called quantum entropy function. In four dimension the near horizon isometry group SL(2,R) x SU(2) for BPS black hole gets enhanced to full SU(1,1,2). Using these enhanced supersymmetries and localization techniques, we will argue that the path integral receives contribution only from special class of field configurations which are invariant under a particular subgroup of SU(1,1,2). We will identify saddle points which are invariant under this subgroup.