Updated project metadata. Protein O-GlcNAcylation is a fast-cycling and nutrient-sensitive post-translational modification (PTM) involved in several functions, including hepatic metabolsm. The substrate of O-GlcNAcylation is UDP-GlcNAc, the end-product of the hexosamine biosynthesis pathway that is initiated by glutamine. O-GlcNAcylation is known to regulate several biochemical processes by modulation of the enzyme activity among other functions, we hypothesized that O-GlcNAcylation regulates the enzyme activity of one or more urea cycle enzymes, a key pathway for waste nitrogen detoxification. To test this notion, we performed immunoprecipitation of male wild-type (C57BL/6) mouse liver lysates with a well-established anti-O-GlcNAc antibody (RL2) followed by mass spectrometry analysis in order to identify proteins undergo this PTM.