  We show that the 5D Nekrasov partition functions enjoy the enhanced global
symmetry of the UV fixed point. The fiber-base duality is responsible for the
global symmetry enhancement. For $SU(2)$ with $N_f\leq 7$ flavors the
fiber-base symmetry together with the manifest flavor $SO(2N_f)$ symmetry
generate the $E_{N_f+1}$ global symmetry, while in the higher rank case the
manifest global symmetry of the two dual theories related by the fiber-base
duality map generate the symmetry enhancement. The symmetry enhancement at the
level of the partition function is manifest once we chose an appropriate
reparametrization for the Coulomb moduli.

High Energy Physics - Theory