Abstract
Nonenzymatic glycosylation or glycation of macromolecules, especially proteins leading to their oxidation, play an important role in diseases. Glycation of proteins primarily results in the formation of an early stage and stable Amadori-lysine product which undergo further irreversible chemical reactions to form advanced glycation endproducts (AGEs). This review focuses these products in lysine rich proteins such as collagen and human serum albumin for their role in aging and age-related diseases. Antigenic characteristics of glycated lysine residues in proteins together with the presence of serum autoantibodies to the glycated lysine products and lysine-rich proteins in diabetes and arthritis patients indicates that these modified lysine residues may be a novel biomarker for protein glycation in aging and age-related diseases.
Highlights
A non-enzymatic glycosylation or Maillard reaction of proteins primarily takes place at ε-amino groups of lysine or their free amino groups
CML is formed by oxidative degradation of Amadori products [50]
To glycation theory, cross linking and denaturation of proteins caused by glycation are the main factors for early aging induced alteration in tissues and blood vessels [44,45]
Summary
A non-enzymatic glycosylation or Maillard reaction of proteins primarily takes place at ε-amino groups of lysine or their free amino groups. Amadori-modified proteins, an early glycation product, undergo further reactions through a number of pathways and giving rise to advanced glycation end products (AGEs) [73,76]. Reactive carbonyl species (RCS), such as glyoxal, formed from autoxidative degradation of glucose and from other metabolic activities, react with lysine residues of proteins to form Nε-carboxymethyllysine (CML), a nonfluorescent and non-cross linking AGE [15]. To glycation theory, cross linking and denaturation of proteins caused by glycation are the main factors for early aging induced alteration in tissues and blood vessels [44,45]. We shall discuss the evidences that support the role of glycated (AGE and Amadori products) lysine residues of proteins in aging and age-related diseases. Antigenicity of the glycated proteins and presence of autoantibodies against native and modified proteins, in age associated diseases, will be considered for the discussion
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