L lysine

l‐Lysine and 5‐aminopentanoate were purchased from Tokyo Chemical Industry Co., Ltd. (https://www.tcichemicals.com); cadaverine, δ‐valerolactam, 1‐formylpyrrolidine, 1,9‐diaminononane and β‐nicotinamide adenine dinucleotide (NAD⁺) were obtained from Sigma‐Aldrich (http://www.sigmaaldrich.com); 5‐aminopentanal was acquired from Activate Scientific (https://shop.activate-scientific.com); [α‐¹⁵N]‐l‐Lysine and [ε‐¹⁵N]‐l‐lysine were purchased from Cambridge Isotope Laboratories Inc. (http://www.isotope.com); l‐ornithine, putrescine and all LC‐MS‐grade buffers used for LC‐MS were purchased from FUJIFILM Wako Pure Chemical Co. (http://www.wako-chem.co.jp).

SCAAs (Cys, CySS, GSH, and HCys), 1,4-benzoquinone (pBQ), 3-mercaptopropionic acid (3-MPA), PR, BPR, PV, and other amino acids [L–alanine (Ala), L–arginine (Arg), L–aspartic acid (Asp), L–glutamine (Gln), L–glutamic acid (Gln), glycine (Gly), L–histidine (His), L–isoleucine (Ile), L–leucine (Leu), L–lysine (Lys), L–methionine (Met), L–phenylalanine (Phe), L–proline (Pro), L–serine (Ser), L–threonine (Thr), L–tryptophan (Trp), L–tyrosine (Tyr), and L–valine (Val)] were purchased from Tokyo Chemical Industries Co. Inc. (Tokyo, Japan). Additionally, ARS, sodium chloride, methanol, and zinc nitrate hexahydrate were purchased from FUJIFILM Wako Pure Chemical Co. Inc. (Osaka, Japan). N-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) was purchased from Dojindo Laboratories (Kumamoto, Japan). All chemicals were used without further purification. All aqueous samples were prepared with Milli-Q water (18.2 MΩcm) (Millipore, Bedford, MA, United States).