Lapolla Annunziata, Brancia Francesco L, Bereszczak Jessica, Fedele Domenico, Baccarin Lorenzo, Seraglia Roberta, Traldi Pietro
Dipartimento di Scienze Mediche e Chirurgiche, Università di Padova, Italy.
Mol Nutr Food Res. 2007 Apr;51(4):456-61. doi: 10.1002/mnfr.200600291.
Advanced glycation end-product (AGE)/peptides, arising from in vivo digestion of glycated proteins, are biologically important compounds, due to their reactivity against circulating and tissue proteins. For information on their possible structure, in vitro glycation of HSA and its further enzymatic digestion were performed. The resulting digestion product mixture was analysed directly by MALDI MS with various matrices [2,5-dihydroxy benzoic acid (DHB) and alpha-cyano-4-hydroxy cinnamic acid (CHCA)]. Alternatively, offline microbore LC prior to MALDI analysis was used, and showed that 63% of the free amino groups prone to glycation are modified, indicating the contemporary presence of unglycated peptides. This result proves that, regardless of the high glucose concentration employed for HSA incubation, glycation does not go to completion. Further studies showed that the collisionally activated decomposition of singly charged glycated peptides leads to specific fragmentation pathways, all related to the condensed glucose molecule. These unique product ions can be used as effective markers to establish the presence of a glucose molecule within a peptide ion.
晚期糖基化终产物（AGE）/肽是糖化蛋白质在体内消化产生的，由于它们对循环蛋白和组织蛋白具有反应活性，因而属于具有重要生物学意义的化合物。为了解其可能的结构，对人血清白蛋白（HSA）进行了体外糖基化及其后续的酶解。所得的酶解产物混合物直接用基质辅助激光解吸电离质谱（MALDI MS）结合各种基质[2,5-二羟基苯甲酸（DHB）和α-氰基-4-羟基肉桂酸（CHCA）]进行分析。或者，在MALDI分析之前采用离线微径液相色谱（LC），结果显示63%易于糖基化的游离氨基被修饰，这表明同时存在未糖基化的肽段。该结果证明，无论用于HSA孵育的葡萄糖浓度多高，糖基化都不会完全发生。进一步研究表明，单电荷糖基化肽的碰撞激活分解会产生特定的碎裂途径，所有这些途径都与缩合葡萄糖分子有关。这些独特的产物离子可作为有效的标志物，用于确定肽离子中葡萄糖分子的存在。
