  In this paper we derive Ward-Takahashi identities from the path integral of
supersymmetric five-dimensional field theories with an $SU(1,3)$ spacetime
symmetry in the presence of instantons. We explicitly show how $SU(1,3)$ is
enhanced to $SU(1,3)\times U(1)$ where the additional $U(1)$ acts
non-perturbatively. Solutions to such Ward-Takahashi identities were previously
obtained from correlators of six-dimensional Lorentzian conformal field
theories but where the instanton number was replaced by the momentum along a
null direction. Here we study the reverse procedure whereby we construct
correlation functions out of towers of five-dimensional operators which satisfy
the Ward-Takahashi identities of a six-dimensional conformal field theory. This
paves the way to computing observables in six dimensions using five-dimensional
path integral techniques. We also argue that, once the instanton sector is
included into the path integral, the coupling of the five-dimensional
Lagrangian must be quantised, leaving no free continuous parameters.
