Identification of N⁷-(1-carboxyethyl)-arginine, a novel posttranslational protein modification of arginine formed at high hydrostatic pressure

An aqueous solution of N^α-acetylarginine (0.1 mol/L) and glucose (0.3 mol/L) in 0.5 mol/L 3-[N-morpholino]propanesulfonic acid (5 mL; pH 7.0) was incubated at 110°C for 2 h with application of high hydrostatic pressure (HHP). After enzymic deacetylation, the arginine modifications formed were separated by ion exchange chromatography. Besides N⁵-(4,5- dihydro-4-methyl-5-oxo-1H-imidazol-2-yl)-L-ornithine, the novel arginine modification N⁷-(1-carboxyethyl)-arginine was identified based on NMR and LC/MS measurements and synthesis-in particular, in samples reacted at a pressure of 600 MPa. As compared to samples treated at normal pressure, both compounds were formed in higher amounts at increased pressure.