biostudies-literatureChikazawa MMEXT | Japan Society for the Promotion of ScienceJapan Agency for Medical Research and Development7697-7709https://www.ebi.ac.uk/biostudies/studies/S-EPMC7261792biostudies-literatureUnknown295(22)Lysine <i>N</i>-pyrrolation converts lysine residues to <i>N</i>^ϵ-pyrrole-l-lysine (pyrK) in a covalent modification reaction that significantly affects the chemical properties of proteins, causing them to mimic DNA. pyrK in proteins has been detected <i>in vivo</i>, indicating that pyrrolation occurs as an endogenous reaction. However, the source of pyrK remains unknown. In this study, on the basis of our observation <i>in vitro</i> that pyrK is present in oxidized low-density lipoprotein and in modified proteins with oxidized polyunsaturated fatty acids, we used LC-electrospray ionization-MS/MS coupled with a stable isotope dilution method to perform activity-guided separation of active molecules in oxidized lipids and identified glycolaldehyde (GA) as a pyrK source. The resulThe Journal of biological chemistryGlycolaldehyde is an endogenous source of lysine <i>N</i>-pyrrolation.PMC72617922611101118gm0910013h000217H06170Chikazawa MNegishi LYoshitake JShibata TIwata SLim SYUchida KfalseGlycolaldehyde is an endogenous source of lysine <i>N</i>-pyrrolation.Lysine <i>N</i>-pyrrolation converts lysine residues to <i>N</i>^ϵ-pyrrole-l-lysine (pyrK) in a covalent modification reaction that significantly affects the chemical properties of proteins, causing them to mimic DNA. pyrK in proteins has been detected <i>in vivo</i>, indicating that pyrrolation occurs as an endogenous reaction. However, the source of pyrK remains unknown. In this study, on the basis of our observation <i>in vitro</i> that pyrK is present in oxidized low-density lipoprotein and in modified proteins with oxidized polyunsaturated fatty acids, we used LC-electrospray ionization-MS/MS coupled with a stable isotope dilution method to perform activity-guided separation of active molecules in oxidized lipids and identified glycolaldehyde (GA) as a pyrK source. The resul2020-01-01T00:00:00Z2020 May2025-05-18T12:04:34.499Z2025-05-18T12:04:34.499ZS-EPMC72617923233209410.1074/jbc.RA120.01317910.1074/jbc.ra120.013179