Yeboah F K, Alli I, Yaylayan V A, Konishi Y, Stefanowicz P
Department of Food Science and Agricultural Chemistry, Macdonald Campus of McGill University, 21,111 Lakeshore Road, Ste. Anne de Bellevue, Quebec, Canada H9X 3V9.
J Agric Food Chem. 2000 Jul;48(7):2766-74. doi: 10.1021/jf990978j.
Electrospray ionization mass spectrometry (ESI-MS) was used to study the glycation of lysozyme by D-glucose (LZM-G) and by D-fructose (LZM-F) under dry heating conditions in the presence and in the absence of oxygen. ESI-MS proved to be a precise method for monitoring protein glycation with respect to following the extent of glycation and changes in the glycoconjugate profile with time. The ESI-MS spectrum of glycated LZM revealed a heterogeneous distribution of glycoforms of LZM at different reaction stages. D-Glucose showed a higher level of reactivity with the amino groups of LZM than D-fructose, both in the presence and in the absence of oxygen. The presence of oxygen in the reaction system induced oxidative side reactions, which competed with and slowed the initial rate of formation of Amadori or Heyns products. The more reactive glycoxidation products formed during the initial stages of incubation in the presence of oxygen accelerated the rate of glycation during the later stages of incubation and increased the involvement of arginine residues of LZM in the glycation reaction. The interaction between the initial glycoxidation product(s) of the reducing sugars and intact lysozyme during the later stages of incubation was observed by the appearance of a different cluster of glycoconjugates in the mass spectrum during the latter stages of incubation. The molecular weight differences between the molecular ions of the new cluster of glycoconjugates are consistent with the formation of D-glucosone from the autoxidation of D-glucose or from the oxidative cleavage of the glucose-lysozyme imine adduct in the lysozyme-glucose system. The effect of oxygen-induced glycoxidation on the glycation reaction was also more pronounced in the LZM-G system compared with that in the LZM-F system.
采用电喷雾电离质谱法（ESI-MS）研究了在有氧气和无氧气存在的情况下，干燥加热条件下D-葡萄糖（LZM-G）和D-果糖（LZM-F）对溶菌酶的糖基化作用。ESI-MS被证明是一种精确的方法，可用于监测蛋白质糖基化过程中糖基化程度以及糖缀合物谱随时间的变化。糖基化溶菌酶的ESI-MS谱显示，在不同反应阶段，溶菌酶糖型呈异质分布。无论有无氧气存在，D-葡萄糖与溶菌酶氨基的反应活性均高于D-果糖。反应体系中氧气的存在引发了氧化副反应，该反应与Amadori或Heyns产物的初始形成速率竞争并使其减慢。在有氧气存在的孵育初始阶段形成的反应性更强的糖氧化产物，在孵育后期加速了糖基化速率，并增加了溶菌酶精氨酸残基参与糖基化反应的程度。在孵育后期，通过质谱中出现不同的糖缀合物簇，观察到了还原糖的初始糖氧化产物与完整溶菌酶之间的相互作用。新糖缀合物簇的分子离子之间的分子量差异与D-葡萄糖自氧化或溶菌酶-葡萄糖体系中葡萄糖-溶菌酶亚胺加合物的氧化裂解形成D-葡萄糖酮一致。与LZM-F体系相比，氧气诱导的糖氧化对LZM-G体系糖基化反应的影响也更为明显。
