Glycation, of proteins

Ortwerth BJ, Chemoganskiy V Mossine VV Olesen PR. The effect of UVA light on the anaerobic oxidation of ascorbic acid and the glycation of proteins. Invest Ophthalmol Vis Sci 2003 44 3094-3102. 

Thornalley PJ, Langborg A, Minhas FIS (1999), Formation of glyoxal, methylglyoxal and 3-deoxyglucosone in the glycation of proteins by glucose, Biochem J. 344 109-116. 

Figure 32-1. (A) Schematic representation of the nonenzymatic glycation of proteins, including hemoglobin, resulting in glycated HbAlc. (B) Chemical structure of advanced glycation end products in tissues exposed to chronic hyperglycemia.The R groups designate tissue proteins that have become cross-linked and frequently become dysfunctional as a result of this process. Adapted from Brownlee (1992).

The Maillard reaction describes the nonenzymic glycation of proteins (Fig. 6). 

A number of studies have suggested that vitamin Bg may he effective in preventing the adverse effects of poor glycemic control that lead to the development of the complications of diabetes mellitus (Jain and Lim, 2001). Many of these effects are mediated hy nonenzymic glycation of proteins. Target proteins include the following ... 

The vital role of insulin is best appreciated when we look at the consequences of a lack of insulin and/or a lack of insulin response, leading to excess blood glucose. Hyperglycaemia is responsible for many manifestations of the disease, because it leads to non-enzymic glycation of proteins, as shown by Anthony Cerami (of course, there are other important manifestations of the disease, such as the dysfunction of fatty acid metabolism and the formation of ketone bodies, which have not been considered here see P. J. Randle et... 

A number of organogermaitium derivatives have been prepared and tested for anticancer activityStudies to test efficacy against a number of other diseases have also been explored.In particular, the dramatic claim has been made that 2-carboxyethylgermasesquioxane (Ge-132) inhibits the MaUlard reaction which is responsible for the glycation of proteins in vivo. Protein glycation by this reaction may be related to diseases such as diabetes and Alzheimer s disease. 

Derived from oxidative modification of triose phosphate during glucose metabolism model for glycation of proteins reacts with amino groups in proteins and nucleic acids involved in advanced glycation endproducts. 

What are the molecular and clinical consequences of glycation of proteins ... 

Water is necessarily a medium of choice for glycation of proteins, although aqueous syrups were successfully employed for syntheses of small D-fructosamines as well. ° Food proteins, most often casein or lactoglobulin, have been purportedly modified by reducing saccharides, in order to improve their solubility, thermal stability, emulsifying properties, or to reduce the allergenicity. The reaction is carried out in the solid phase and with controlled humidity.Optimal conditions for formation of the protein Amadori product from lyophilized protein-carbohydrate mixtures are 55-60 °C, water activity = 0.44-0.65, carbohydrate-protein molar ratio >2. 

I. Penndorf, C. Li, U. Schwarzenbolz, and T. Henle, N-tenninal glycation of proteins and peptides in foods and in vivo Evaluation of iV-(2-furoylme(hyl)valine in acid hydrolyzates in human hemoglobin, Ann. N. Y. Acad. Sci., 1126 (2008) 118-123. 

Vitamin E and other free radical scavengers have been shown to inhibit the glycation of proteins, in vivo and in vitro (Rosen et aL, 1991 Ceriello et al., 1991 Aoki et al., 1992 LeGuen et al., 1992). This might also apply to ascorbylation of proteins, given that the effect of such free radical scavengers is likely to be inhibition of enediol-mediated oxidant formation which involves an enediol-radical intermediate (Hunt, 1994), shown in Figs. 6 and 8. 

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