Comprehensive Analysis of Maillard Protein Modifications in Human Lenses: Effect of Age and Cataract

Smuda, Mareen; Henning, Christian; Raghavan, Cibin T.; Johar, Kaid; Vasavada, Abhay R.; Nagaraj, Ram H.; Glomb, Marcus A.

doi:10.1021/bi5013194

Cited by 77 publications

(138 citation statements)

References 42 publications

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“…␣-Dicarbonyls are major precursors of AGEs (14). Several ␣-dicarbonyls, such as methylglyoxal and glyoxal, have been extensively studied in AGE formation (41).…”

Section: Discussionmentioning

confidence: 99%

“…Enzymatic digestion of lens proteins was performed as described previously with some minor modifications (14). Five hundred micrograms of freeze-dried protein was dissolved in 150 l of PBS, and one small crystal of thymol was added.…”

Section: Enzymatic Digestion Of Proteins For Age Analysismentioning

confidence: 99%

“…To this solution, 0.1 units of Pronase E (two additions), 0.3 units of leucine aminopeptidase, and 0.3 units of carboxypeptidase Y were added stepwise at 24-h intervals for 96 h. Finally, the sample was filtered through a 3 kDa cut-off filter (VWR, Radnor, PA). To determine protein digestion efficiency, we compared the N ⑀ -carboxymethyllysine levels in the enzyme digests with those in acid hydrolysates of the same sample and considered N ⑀ -carboxymethyllysine levels in acid-hydrolyzed samples to represent 100% efficiency of hydrolysis, as described previously (14). A sample aliquot was diluted with an equal volume of acetonitrile prior to UPLC-MS 2 analysis (method 3).…”

Section: Enzymatic Digestion Of Proteins For Age Analysismentioning

confidence: 99%

“…The oxidation products of ascorbate have long been known to undergo the Maillard reaction with proteins to form advanced glycation end products (AGEs) 2 (13). Several AGEs have been shown to occur in human lenses (3,14). AGEs are formed as protein cross-linking and non-cross-linking adducts; many of them are fluorescent and yellow chromophores with characteristics similar to those of proteins found in aged and cataractous lenses (15).…”

mentioning

confidence: 99%

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Identification of Kynoxazine, a Novel Fluorescent Product of the Reaction between 3-Hydroxykynurenine and Erythrulose in the Human Lens, and Its Role in Protein Modification

Rakete

Nagaraj

2016

Journal of Biological Chemistry

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Kynurenine pathway metabolites and ascorbate degradation products are present in human lenses. In this study, we showed that erythrulose, a major ascorbate degradation product, reacts spontaneously with 3-hydroxykynurenine to form a fluorescent product. Structural characterization of the product revealed it to be 2-amino-4-(2-hydroxy-3-(2-hydroxyethyl)-2H-benzo[b][1, 4]oxazin-5-yl)-4-oxobutanoic acid, which we named kynoxazine. Unlike 3-hydroxykynurenine, 3-hydroxykynurenine glucoside and kynurenine were unable to form a kynoxazine-like compound, which suggested that the aminophenol moiety in 3-hydroxykynurenine is essential for the formation of kynoxazine. This reasoning was confirmed using a model compound, 1-(2-amino-3-hydroxyphenyl)ethan-1-one, which is an aminophenol lacking the amino acid moiety of 3-hydroxykynurenine. Ultra-performance liquid chromatography-tandem mass spectrometry analyses showed that kynoxazine is present in the human lens at levels ranging from 0 to 64 pmol/mg lens. Kynoxazine as well as erythrulose degraded under physiological conditions to generate 3-deoxythreosone, which modified and cross-linked proteins through the formation of an arginine adduct, 3-deoxythreosone-derived hydroimidazolone, and a lysine-arginine cross-linking adduct, 3-deoxythreosone-derived hydroimidazolimine cross-link. Ultra-performance liquid chromatography-tandem mass spectrometry quantification showed that 32-169 pmol/mg protein of 3-deoxythreosone-derived hydroimidazolone and 1.1-11.2 pmol/mg protein of 3-deoxythreosone-derived hydroimidazolimine cross-link occurred in aging lenses. Taken together, these results demonstrate a novel biochemical mechanism by which ascorbate oxidation and the kynurenine pathway intertwine, which could promote protein modification and cross-linking in aging human lenses.

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“…␣-Dicarbonyls are major precursors of AGEs (14). Several ␣-dicarbonyls, such as methylglyoxal and glyoxal, have been extensively studied in AGE formation (41).…”

Section: Discussionmentioning

confidence: 99%

Section: Enzymatic Digestion Of Proteins For Age Analysismentioning

confidence: 99%

Section: Enzymatic Digestion Of Proteins For Age Analysismentioning

confidence: 99%

mentioning

confidence: 99%

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Identification of Kynoxazine, a Novel Fluorescent Product of the Reaction between 3-Hydroxykynurenine and Erythrulose in the Human Lens, and Its Role in Protein Modification

Rakete

Nagaraj

2016

Journal of Biological Chemistry

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“…Ascorbate has been shown to glycate lens proteins with eventual formation of advanced glycated end products known to be associated with lens aging and cataract formation [12]. Additionally, since ascorbate and tocopherols are not of endogenous nature, they are required to be continuously supplemented in the diet.…”

Section: Research Articlementioning

confidence: 99%

Stimulation of Glycolysis in the Lens by Pyruvate. Implications in Protection against Oxidative Stress

Hegde¹,

Varma²

2015

J Metabolic Synd

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Objective: We have previously demonstrated that pyruvate protects the lens against oxidative stress in vitro as well as prevents cataract formation in vivo induced by oxidative stress. The effects have been attributed to its property of scavenging various reactive oxygen species (ROS). Additionally we hypothesize that the preventive effect is also due to its effect of stimulating glycolysis.Methods: This has been tested as follows: freshly isolated mice lenses were incubated for 4 hours in Tyrode medium containing 5-3 H-glucose as a tracer in the presence and absence of 2 mM sodium pyruvate and determining generation of 3 H2O and 3 H-lactate separated by column chromatography in succession through homemade anion exchange column followed by the phenylboronate and formate mini-columns.Results: the concentration of 3 H 2 O in the medium at the end of incubation was 95 µM in the controls incubated without pyruvate. In the presence of pyruvate (2 mM) added to the medium, the concentration of 3 H 2 O attained in the medium was 152 µM. The corresponding value expressed on the basis of lens weight was 46 nanomoles/lens in the control group vs. 88 nanomoles/lens with 2 mM pyruvate. Conclusion:As hypothesized, pyruvate was found to stimulate glycolysis in the lens as indicated by the enhanced generation of both 3 H 2 O and 3 H-lactate in lenses incubated in its presence as compared to controls. The observed metabolic stimulation is attributed to recycling of NAD generated during the reduction of pyruvate to lactate, NAD being the required cofactor in the oxidation of glyceraldehyde-3-phosphate to 1,3-diphosphoglycerate. That such stimulation is involved in its protective effect is also apparent by our previous reports showing higher ATP levels in the lenses cultured in medium generating ROS in the presence of pyruvate than in its absence, the primary source of ATP in lens being glycolysis.

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The M aillard Reaction: Protein Modification by Ascorbic Acid

Monnier

Sell

Hom

et al. 2021

Long‐lived Proteins in Human Aging and Disease

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Comprehensive Analysis of Maillard Protein Modifications in Human Lenses: Effect of Age and Cataract

Cited by 77 publications

References 42 publications

Identification of Kynoxazine, a Novel Fluorescent Product of the Reaction between 3-Hydroxykynurenine and Erythrulose in the Human Lens, and Its Role in Protein Modification

Identification of Kynoxazine, a Novel Fluorescent Product of the Reaction between 3-Hydroxykynurenine and Erythrulose in the Human Lens, and Its Role in Protein Modification

Stimulation of Glycolysis in the Lens by Pyruvate. Implications in Protection against Oxidative Stress

The M aillard Reaction: Protein Modification by Ascorbic Acid

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