Photochemistry of a polyaromatic hydrocarbon, pyrene C16H10, with water has been investigated at cryogenic temperatures. Photoprocessing of this species, performed at lambda > 235 nm, in argon matrices, adsorbed onto amorphous water surfaces, and trapped in solid water, led to the formation of ketonic isomers, C16H10O, and possibly quinones. These species have been identified for the first time by infrared spectroscopy with the support of isotopic substitution experiments and DFT calculations. These oxidized pyrene-like species, of atmospherical and astrochemical interest, most likely arise from a tautomeric rearrangement of their analogous hydroxylated molecules, these latter being formed by reaction of water with pyrene cations.