Glycation of N-ε-carboxymethyllysine

Abstract

The Maillard reaction is traditionally subdivided into three stages that start consecutively and run in parallel. Here, we show that N-ε-carboxymethyllysine (CML), a compound formed in the late stage of the reaction, can undergo a second glycation event at its secondary amino group leading to a new class of Amadori rearrangement products. When N-α-hippuryl-CML was incubated in the presence of reducing sugars such as glucose, galactose, ribose, xylose, maltose, or lactose in solution for 1 h at 75 °C, the compound was degraded by 6–21%, and N-ε-carboxymethyl-N-ε-deoxyketosyl lysine derivatives were formed. Under the same conditions, lysine was 5–10 times more reactive than CML. N-α-hippuryl-N-ε-carboxymethyl-N-ε-(1-deoxyfructosyl)-l-lysine (hippuryl-CMFL) and N-ε-carboxymethyl-N-ε-(1-deoxyfructosyl)-l-lysine (CMFL) were synthesized, isolated and characterized by MS/MS and NMR experiments. Depending on the reaction conditions, up to 21% of CMFL can be converted to the furosine analogue N-ε-carboxymethyl-N-ε-furoylmethyl-l-lysine (CM-Fur) during standard acid protein hydrolysis with hydrochloric acid. Incubation of bovine serum albumin (BSA) with glucose for up to 9 weeks at 37 °C revealed the formation of CMFL in the protein as assessed by HPLC–MS/MS in the MRM mode. Under these conditions, ca. 13% of lysine residues had been converted to fructosyllysine, and 0.03% had been converted to CMFL. The detection of glycation products of glycated amino acids (heterogeneous multiple glycation) reveals a novel pathway in the Maillard reaction.

CIGB-258 Exerts Potent Anti-Inflammatory Activity against Carboxymethyllysine-Induced Acute Inflammation in Hyperlipidemic Zebrafish via the Protection of Apolipoprotein A-I

“…A recent report suggested that the CML can undergo a second glycation event at its secondary amino group, leading to a new class of Amadori rearrangement products [ 40 ]. Glycated amino acids, such as CML, are not inert molecules because CML can be degraded and converted into secondary amino groups [ 41 ], which can be subject to second glycation events.…”

Formation of Protein-Bound Maillard Reaction Products during the Storage of Manuka Honey

“…Therefore, 37–42 μmol lysine/mmol leucine (representing 11–13% of the initial lysine residues) reacted to glycation compounds not detected within the experiments. As the formation of further lysine reaction products of the advanced glycation, such as maltosine or N -ε-carboxymethyl- N -ε-fructosyllysine, is only of minor importance, , it can be assumed that the formation of Heyns products from fructose and lysine, which is independent of MGO, , might be responsible for the so far unexplained difference in the lysine modification.…”