Munanairi Admire, O'Banion Steven K, Gamble Ryan, Breuer Elizabeth, Harris Andrew W, Sandwick Roger K
Department of Chemistry and Biochemistry, Middlebury College, Middlebury, VT 05753, United States.
Carbohydr Res. 2007 Dec 10;342(17):2575-92. doi: 10.1016/j.carres.2007.08.003. Epub 2007 Aug 19.
Ribose 5-phosphate (R5P) undergoes the Maillard reaction with amines at significantly higher rates than most other sugars and sugar phosphates. The presence of an intramolecular phosphate group, which catalyzes the early stages of the Maillard reaction, provides the opportunity for the R5P molecule to undergo novel reaction paths creating unique Maillard products. The initial set of reactions leading to an Amadori product (phosphorylated) and to an alpha-dicarbonyl phosphate compound follows a typical Maillard reaction sequence, but an observed phosphate hydrolysis accompanying the reaction adds to the complexity of the products formed. The reaction rate for the loss of R5P is partially dependent on the pK(a) of the amine but also is correlated to the protonation of an early intermediate of the reaction sequence. In the presence of oxygen, a carboxymethyl group conjugated to the amine is a major product of the reaction of R5P with N-acetyllysine while little of this product is generated in the absence of oxygen. Despite lacking a critical hydroxyl group necessary for the Maillard reaction, 2-deoxyribose 5-phosphate (dR5P) still generates an Amadori-like product (with a carbonyl on the C-3 carbon) and undergoes phosphate cleavage. Two highly UV-absorbing products of dR5P were amine derivatives of 5-methylene-2-pyrrolone and 2-formylpyrrole. The reaction of dR5P with certain amines generates a set of products that exhibit an interesting absorbance at 340nm and a high fluorescence.
5-磷酸核糖（R5P）与胺发生美拉德反应的速率明显高于大多数其他糖类和糖磷酸盐。分子内磷酸基团的存在催化了美拉德反应的早期阶段，这为R5P分子开辟了新的反应路径，从而产生独特的美拉德产物。导致生成阿马多里产物（磷酸化的）和α-二羰基磷酸化合物的初始反应遵循典型的美拉德反应序列，但反应过程中观察到的磷酸水解增加了所形成产物的复杂性。R5P损失的反应速率部分取决于胺的pK(a)，但也与反应序列早期中间体的质子化有关。在有氧存在的情况下，与胺共轭的羧甲基是R5P与N-乙酰赖氨酸反应的主要产物，而在无氧条件下几乎不产生这种产物。尽管2-脱氧-5-磷酸核糖（dR5P）缺乏美拉德反应所需的关键羟基，但它仍能生成类似阿马多里的产物（C-3碳上有羰基）并发生磷酸裂解。dR5P的两种高紫外吸收产物是5-亚甲基-2-吡咯酮和2-甲酰基吡咯的胺衍生物。dR5P与某些胺的反应产生了一组在340nm处具有有趣吸光度和高荧光的产物。
