Carboxymethyllysine

Hartkopf, J. and Erbersdobler, H.F. (1995). Model experiments with sausage meat on the formation of 7V -carboxymethyllysine, Z. Lebensm. Unters. Forsch., 201, 27-29. 

The increase of carboxymethyllysine (batch 1) and pentosidine (batches 1 and 11) thus observed provided additional proof for fhe Maillard reaction in caries (fable 3, figs. 2, 3). The pentosidine level ranged from abouf equal fo a manifold of the level in sound dentin. The formation of pentosidine can only account for a fraction of the increase in 328/378 fluorescence, which is in accordance with a major contribution from a different fluorophore as stated above. Unfortunately, an increase of dify-rosine as expected from fhe gain in 317/407 fluorescence (fable 2) could not be substantiated unequivocally by HPLC analysis because dityrosine co-eluted with lysylpyridinoline. Even if we would consider dityrosine to originate the lysylpyridinoline peaks observed in HPLC of carious dentin, but not of sound dentin, only one quarter of the increase in 317/407 fluorescence would derive from difyrosine. 

Al-Abed Y and Bucala R (1995) N-carboxymethyllysine formation by direct addition of glyoxal to lysine during the Maillard reaction. Bioorg Med Chem Lett 5, 2161-2162. 

Liardon R, De Weck-Gaudard D, Philippossian G and Finot P-A (1987) Identification of N-carboxymethyllysine a new Maillard reaction product, in rat urine. J Agr Food Chem 35, 427-431. 

The described conditions alkylate cysteine residues almost quantitatively, even for defensins, which contain three disulfide bonds. Higher temperatures (>37°C) and longer reaction times (> 1 h) do not further increase the cysteine alkylation but may produce further byproducts, such as carboxymethyllysine (CML). 

Carboxymethylethanolamine (CME) has been shown to be present in red blood cell membrane hydrolysates at ca 0.14 mmol mol 1 ethanolamine. Carboxymethyllysine was present in the membrane proteins at ca 0.2 mmol mol-1 lysine, in both cases there being no difference between samples from diabetic (free of complications) and nondiabetic subjects.142 CME was also detected in fasting urine at 2-3 nmol mg 1 of creatinine from samples of both diabetic and nondiabetic subjects. Requena et al.142 calculate a value of the 2.8 //mol CME excreted daily, > 99% arising from the normal turnover of membrane lipids of cells other than RBC. 

R. Liardon, D. de Weck-Gaudard, G. Philippossian, and P.-A. Finot, Identification of Ne-carboxymethyllysine A new Maillard reaction product, in rat, J. Agric. Food Chem.,... 

Homocitrulline elutes from most analyzer columns just prior to valine. Alternatively, the unreacted lysines can be converted under denaturing conditions to other acid-stable derivatives (homoarginine, methyl-lysines, carboxymethyllysines) which can be quantitated after acid hydrolysis (above and 2.12). The homocitrulline content can then be assumed to be the difference between the total lysine content and the content of the acid-stable derivative. Alkaline hydrolysis of carbamylated proteins gives quantitative conversion of homocitrulline to lysine (Stark and Smyth 1963), and this can be used to check the homocitrulline content of the protein in which the other lysines have been converted to another derivative that does not give lysine by alkaline hydrolysis (see also 3.I.2.I.). 

R. Badoud, L. Fay, F. Hunston, and G. Pratz, Periodate oxidative degradation of Amadori compounds. Formation of V -carboxymethyllysine and... 

V. Somoza, E. Wenzel, C. WeiB, 1. Clawin-Radecker, N. GriibeL and H. F. Erbersdobler, Dose-dependent utilisation of casein-linked lysinoalanine, A(epsi-lon)-ihictoselysine and W(epsilon)-carboxymethyllysine in rats. Mol. Nutr. Food Res., 50 (2006) 833-841. 

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