Non-degenerate four-wave mixing effects are investigated in an injection-locked InAs/InP nanostructured Fabry-Perot laser. Locking the pump signal at different wavelengths within the gain curve shows different symmetry between up and down conversions. Experiments prove that the normalized conversion efficiency remains much more symmetric when the pump is locked at shorter wavelengths from the gain peak. The values of nonlinear conversion efficiencies are maintained above -60 dB for pump-probe frequency detunings up to 3.5 THz. The role of the linewidth enhancement factor on the asymmetry is discussed and the value of the nonlinear susceptibility is compared to InAs/InP nanostructured semiconductor optical amplifiers.