  Recently, the IC/CMB X-ray mechanism has been strongly disfavoured for 3C 273
and PKS 0637-752 since the anomalously hard and steady gamma-ray emission
predicted by such models violates the observational results from Fermi-LAT.
Here we propose the proton synchrotron origin of the X ray-gamma ray flux from
the knots of PKS 0637-752 with a reasonable budget in luminosity, by
considering synchrotron radiation from an accelerated proton population.
Moreover, for the source 3C 273, some of the optical data points could not be
explained by electron synchrotron (Meyer et al. 2015), which we have included
in our updated proton synchrotron model. We also show that TeV emission from
large scale quasar jets in principle, can arise from proton synchrotron, which
we discuss in the context of knot wk8.9 of PKS 0637-752.
