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Identification of [6-Hydroxy-2-(hydroxymethyl)-5-oxo-5,6-dihydro‑2H‑pyran-3-yl]-cysteine (HHPC) as a Cysteine-specific Modification Formed from 3,4-Dideoxyglucosone-3-ene (3,4-DGE)

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journal contribution
posted on 14.01.2019, 00:00 by Sabrina Gensberger-Reigl, Lisa Atzenbeck, Alexander Göttler, Monika Pischetsrieder
Glucose degradation products (GDPs) are formed from glucose and other reducing sugars during heat treatment, for example, in heat-sterilized peritoneal dialysis fluids or foods. Because of their reactive mono- and dicarbonyl structure, they react readily with proteins, resulting in the formation of advanced glycation end products (AGEs), loss of protein functionality, and cytotoxicity. Among the GDPs, 3,4-dideoxyglucosone-3-ene (3,4-DGE) exerts the strongest effects despite its relatively low concentration levels. The goal of the present study was therefore to identify the structure of specific protein modifications deriving from 3,4-DGE. A nonapeptide containing the reactive amino acids lysine, arginine, and cysteine was incubated with 3,4-DGE and the dominant GDPs 3-deoxyglucosone (3-DG) and 3-deoxygalactosone (3-DGal) in concentrations as present in peritoneal dialysis fluids (235 μM 3-DG, 100 μM 3-Gal, and 11 μM 3,4-DGE). Glycation rate and product formation were determined by ultra-HPLC–MS/MS (UHPLC–MS/MS). 3,4-DGE showed the strongest glycation activity. After 2 h of incubation, 3,4-DGE had modified 57% of the nonapeptide, whereas 3-DG had modified only 2% and 3-DGal had modified 29% of the peptide. A stable 3,4-DGE-derived cysteine modification was isolated. Its structure was determined by comprehensive NMR and MS experiments to be [6-hydroxy-2-(hydroxymethyl)-5-oxo-5,6-dihydro-2H-pyran-3-yl]-cysteine (HHPC), which represents a novel cysteine–AGE derived from 3,4-DGE. The results indicate that 3,4-DGE might contribute to a severe loss of protein functionality by forming cysteine-specific AGEs, such as HHPC.