The Maillard reaction and oxidative stress during aging of soybean seeds

The chemical reactions that may lead to the loss of seed viability were investigated both during the accelerated aging and natural aging of soybeans ( Glycine max Merrill cv. Chippewa 64). Under conditions of accelerated aging (36°C and 75% RH), fluorescence of soluble proteins accumulated, which was closely correlated with the loss of seed germinability and vigor. We were able to show this correlation by using partially purified proteins for the assay. Fluorescence also increased in seeds under good storage conditions (5°C for up to 21 years), although there was a less significant correlation between seed viability and the accumulation of fluorescent products during the time of natural aging. The rise in protein fluorescence is interpreted as an increase of Maillard products. The carbonyl content of soluble proteins (a measure of the oxidative damage) did not change significantly during either accelerated aging or natural aging: however the elimination of carbonyls during germination seemed to be hindered in seeds that had poor germination. The Maillard reaction may be a consequence of the formation of reducing sugars through a gradual hydrolysis of oligosaccharides during aging. Preliminary evidence from the natural aging study showed that, when seeds were in the glassy state, the sugar hydrolysis was inhibited. These results suggest that the Maillard reaction and oxidative reaction may play an important role in seed deterioration.     

Production and characterization of antibodies to advanced glycation products on proteins

Antibodies directed against advanced glycation products formed during Maillard reaction have been generated and characterized. These antibodies reacted specifically with advanced glycation products in common among proteins incubated with glucose, but not early-stage compounds such as a Schiff base adduct and Amadori rearrangement products. Incubation of bovine serum albumin with glucose caused a time-related increase in immunoreactivity and a concomitant increase in fluorescence intensity. These antibodies may serve as a useful tool to elucidate pathophysiological roles of advanced Maillard reaction in diabetic complications and aging processes.     

衰老研究的新纪元

在人类历史进入２１世纪的时刻,生命科学关于衰老原理的研究迎来了一个划时代的新纪元。多领域、多层次、跨学科的衰老研究,在分子水平上将遗传基因衰老学说、自由基氧化衰老学说、糖基化衰老学说和交联衰老学说汇聚到了一个新的焦点－－羰基毒化衰老学说。由于现代生命科学逐步认识到了羰－－氨反应是诸多生物副反应中的一个核心过程,该反应引起了衰老机理研究了极大重视。     

Mass spectrometric study on the protein chemical modification of uremic patients in advanced Maillard reaction

The Maillard reaction, initiated by the nonenzymatic reaction of reducing sugar with protein, is proposed to play a significant role in protein aging and the complications of aging and diabetes. In this study, we detected and quantified some advanced glycation endproducts (AGEs) in human serum proteins of control and uremic patients by a highly selective and specific assay, electrospray ionization liquid chromatography–mass spectrometry–mass spectrometry (ESI-LC–MS–MS). From our results, levels of each AGEs in serum of uremic patients were significantly elevated, compared to age-matched controls. These results provide the evidence for increased modifications of proteins by Maillard reaction in uremia.     

Relevance of amadori and maillard products to seed deterioration

The possible role of Amadori and Maillard reactions in the deterioration of dry seeds was investigated using model systems and whole soybean seeds, Glycine max cv Hodgson. In model systems of glucose plus an enzyme (lysozyme), the production of Amadori products was accelerated by higher temperature and relative humidity. The reaction between glucose and lysozyme at 50°C, 75% relative humidity, leads to a progressive decline in enzymatic activity. During accelerated aging of soybean seeds (40°C, 100% relative humidity), a sequence is observed in which the Amadori products increase with time and then decline under conditions in which the Maillard products increase in the axes. Loss of germinability occurs at the time when the Maillard products increase in the soybean axes. These results are suggestive of a role for nonenzymic glycation in soybean seed deterioration during accelerated aging.     

Oxygen is not required for the browning and crosslinking of protein by pentoses: relevance to Maillard reactions in vivo

The chemical modification and crosslinking of proteins by the Maillard or browning reaction contributes to the aging of tissue proteins, and acceleration of this reaction during hyperglycemia is implicated in the pathogenesis of diabetic complications. Metal-catalyzed autoxidation reactions catalyze the browning of proteins by glucose, a process known as autoxidative glycosylation, but the effects of oxidative conditions on browning of proteins by smaller sugars has not been reported. In this work we studied the browning and crosslinking of the model protein, RNase A, by pentoses. Although antioxidative conditions inhibited the formation of glyoxal and the advanced glycation end-product, N epsilon-(carboxymethyl)lysine from arabinose, browning and crosslinking, and formation of the fluorescent crosslink pentosidine proceeded at comparable rates under oxidative and antioxidative conditions. These studies and other work on smaller dicarbonyl compounds indicate that Maillard reactions of simpler carbohydrates proceed efficiently in the absence of oxygen and suggest that antioxidant therapy for treatment of diabetic complications may have limited clinical efficacy.     

Premature aging in uremia

Guanidinosuccinic acid is an aberrant metabolite isolated 40 years ago in the blood and urine of uremic subjects and a suspect in the toxicity associated with renal failure. It plays a minor role in the bleeding diathesis of uremia, contributes to the methyl group deficiency of dialysis patients, and is a factor in the premature atherosclerosis of end stage renal disease through the induction of hyperhomocysteinemia. As a major player, however, in the diversity and severity of uremic symptoms, it is a disappointment. Recently its source has been identified. It results from the superoxidation of argininosuccinic acid, which leads, also, to the production of gamma glutamic semialdehyde, an advanced glycation end product (AGE), which normally results from from the Maillard reaction, the non-enzymatic browning of protein. AGEs stimulate cross-linkages in protein that lead ultimately to loss of function, phagocytosis, and removal, and are important elements in the premature aging characteristic of renal disease, and diabetes.     

衰老及相关基因群

综述20世纪与基因相关的衰老原理的探索及其进展,整体动物水平的衰老研究归纳了衰老了诸多表象但疏于对衰老本质的探讨。线粒体－自由基衰老学说阐述了线粒体DNA的损伤与衰老有很大的相关性,由Hayflic k分裂限制衍生的端粒衰老学说给衰老机制提供了重要信息,目前狭隘的基因程序化衰老学说已和损伤衰老概念有机的联系在了一起。总之,自由基衰老学说得到了氧化衰老学说和糖基化衰老学说的补充逐渐形成了生化副反应与基因衰老学说的大统一衰老机制板块理论。     

酚类抗氧化剂对Maillard反应的影响及其作用机制

Maillard反应是食品加工和贮藏过程中发生的重要而最复杂的反应,在食品风味物质形成中发挥积极作用,但近二三十年来的研究也发现它可能存在的食品安全隐患。Maillard反应受氨基和羰基物质组成的影响,但其他物质对Maillard反应的干扰作用研究不多。本文综述了Maillard反应过程中抗氧化活性物质和自由基形成的特点,以及外源酚类可能在丙烯酰胺、呋喃、羟甲基糠醛等有害物质形成中发生的作用;在此基础上,提出了今后应研究的科学问题。     

Formation of S-(carboxymethyl)-cysteine in rat liver mitochondrial proteins: effects of caloric and methionine restriction

Maillard reaction contributes to the chemical modification and cross-linking of proteins. This process plays a significant role in the aging process and determination of animal longevity. Oxidative conditions promote the Maillard reaction. Mitochondria are the primary site of oxidants due to the reactive molecular species production. Mitochondrial proteome cysteine residues are targets of oxidative attack due to their specific chemistry and localization. Their chemical, non-enzymatic modification leads to dysfunctional proteins, which entail cellular senescence and organismal aging. Previous studies have consistently shown that caloric and methionine restrictions, nutritional interventions that increase longevity, decrease the rate of mitochondrial oxidant production and the physiological steady-state levels of markers of oxidative damage to macromolecules. In this scenario, we have detected S-(carboxymethyl)-cysteine (CMC) as a new irreversible chemical modification in mitochondrial proteins. CMC content in mitochondrial proteins significantly correlated with that of the lysine-derived analog N ^ε-(carboxymethyl)-lysine. The concentration of CMC is, however, one order of magnitude lower compared with CML likely due in part to the lower content of cysteine with respect to lysine of the mitochondrial proteome. CMC concentrations decreases in liver mitochondrial proteins of rats subjected to 8.5 and 25 % caloric restriction, as well as in 40 and 80 % methionine restriction. This is associated with a concomitant and significant increase in the protein content of sulfhydryl groups. Data presented here evidence that CMC, a marker of Cys-AGE formation, could be candidate as a biomarker of mitochondrial damage during aging.     

果蔬制品中的美拉德反应及其控制方法研究进展

美拉德反应是一种普遍存在于果蔬制品加工和贮藏过程中的非酶促类褐变反应,其反应机制复杂,会引起褐变,破坏产品感官品质,降低食用价值,还会生成有毒有害物质,危害人体健康。本文对果蔬制品中美拉德反应的历程、影响因素和抑制手段进行归纳总结,对目前研究存在的问题进行展望,以期为果蔬制品中美拉德反应的控制提供参考。     

Peptide and amino acid glycation: new insights into the Maillard reaction.

Nonenzymatic glycation of proteins, peptides and other macromolecules (the Maillard reaction) has been implicated in a number of pathologies, most clearly in diabetes mellitus. but also in the normal processes of aging and neurodegenerative amyloid diseases such as Alzheimer's. In the early stage, glycation results in the formation of Amadori-modified proteins. In the later stages, advanced glycation end products (AGE) are irreversibly formed from Amadori products leading to the formation of reactive intermediates, crosslinking of proteins, and the formation of brown and fluorescent polymeric materials. Although, the glycation of structural proteins has been attributed a key role in the complications of diabetes, recent attention has been devoted to the physiological significance of glycated peptide hormones. This review focuses on the physico-chemical properties of the Amadori compounds of bioactive peptides of endogenous and exogenous origin, such as Leu-enkephalin and morphiceptin, investigated under different conditions as well as on novel pathways in the Maillard reaction observed from investigating intramolecular events in ester-linked glycopeptides.     

Detection of nonenzymatic browning products in the human lens

The nonenzymatic browning or Maillard reaction is an aging process in stored foods. The initial stage of this reaction, nonenzymatic glycosylation, has been shown to occur in the human lens. The possible occurrence of further steps of the Maillard reaction involving lysine residues and glucose has been investigated. A lipid-free protein extract from a pool of human cataractous lenses was reduced, alkylated, and digested with pronase. The digest was reduced with [³H]borohydride, acid hydrolyzed and fractionated by Sephadex G-15 chromatography. The fractions eluting ahead of ?-1-deoxyglucitolyllysine were pooled and separated with an amino acid analyzer. Four fluorescent, yellow, and radioactive peaks were obtained. One of these, which co-eluted with tyrosine, was isolated, acetylated, and further analyzed by reverse phase chromatography using HPLC. Two new peaks were separated which co-chromatographed with lysine derivatives isolated from the nonenzymatic browning reaction of α-tert-butyloxycarbonyllysine with glucose. Control experiments showed that they were not artifacts due to acid hydrolysis of ?-glucitolyllysine. These results suggest that dehydration and rearrangement of the Amadori product, ?-fructosyllysine, has occured in vivo, thus leading to the formation of at least two nonenzymatic browning products.     

Effect of pyridoxamine on chemical modification of proteins by carbonyls in diabetic rats: characterization of a major product from the reaction of pyridoxamine and methylglyoxal

Advanced glycation end products (AGEs) from the Maillard reaction contribute to protein aging and the pathogenesis of age- and diabetes-associated complications. The alpha-dicarbonyl compound methylglyoxal (MG) is an important intermediate in AGE synthesis. Recent studies suggest that pyridoxamine inhibits formation of advanced glycation and lipoxidation products. We wanted to determine if pyridoxamine could inhibit MG-mediated Maillard reactions and thereby prevent AGE formation. When lens proteins were incubated with MG at 37 degrees C, pH 7.4, we found that pyridoxamine inhibits formation of methylglyoxal-derived AGEs concentration dependently. Pyridoxamine reduces MG levels in red blood cells and plasma and blocks formation of methylglyoxal-lysine dimer in plasma proteins from diabetic rats and it prevents pentosidine (an AGE derived from sugars) from forming in plasma proteins. Pyridoxamine also decreases formation of protein carbonyls and thiobarbituric-acid-reactive substances in plasma proteins from diabetic rats. Pyridoxamine treatment did not restore erythrocyte glutathione (which was reduced by almost half) in diabetic animals, but it enhanced erythrocyte glyoxalase I activity. We isolated a major product of the reaction between MG and pyridoxamine and identified it as methylglyoxal-pyridoxamine dimer. Our studies show that pyridoxamine reduces oxidative stress and AGE formation. We suspect that a direct interaction of pyridoxamine with MG partly accounts for AGE inhibition.     

Distinct energy requirement for nuclear import and export of importin beta in living cells

Carbohydrates with reactive aldehyde and ketone groups can undergo Maillard reactions with proteins to form advanced glycation end products. Oxalate monoalkylamide was identified as one of the advanced glycation end products formed from the Maillard reaction of ascorbate with proteins. In these experiments, we have analyzed human lens proteins immunochemically for the presence of oxalate monoalkylamide. Oxalate monoalkylamide was absent in most of the very young lenses but was present in old and cataractous lenses. The highest levels were found in senile brunescent lenses. Incubation experiments using bovine lens proteins revealed that oxalate monoalkylamide could form from the ascorbate degradation products, 2,3-diketogulonate and L-threose. These data provide the first evidence for oxalate monoalkylamide in vivo and suggest that ascorbate degradation and its binding to proteins are enhanced during lens aging and cataract formation.     

Inhibitory effect of Maillard reaction products on growth of the aerobic marine hyperthermophilic archaeon Aeropyrum pernix

It was found that the growth of Aeropyrum pernix was severely inhibited in a medium containing reducing sugars and tryptone due to the formation of Maillard reaction products. The rate of the Maillard browning reaction was markedly enhanced under aerobic conditions, and the addition of Maillard reaction products to the culture medium caused fatal growth inhibition.     

Maillard reaction products in tissue proteins: New products and new perspectives

Summary. The chemical modification of protein by nonenzymatic browning or Maillard reactions increases with age and in disease. Maillard products are formed by reactions of both carbohydrate- and lipid-derived intermediates with proteins, leading to formation of advanced glycation and lipoxidation end-products (AGE/ALEs). These modifications and other oxidative modifications of amino acids increase together in proteins and are indicators of tissue aging and pathology. In this review, we describe the major pathways and characteristic products of chemical modification of proteins by carbohydrates and lipids during the Maillard reactions and identify major intersections between these pathways. We also describe a new class of intracellular sulfhydryl modifications, Cys-AGE/ALEs, that may play an important role in regulatory biology and represent a primitive link between nonenzymatic and enzymatic chemistry in biological systems.     

Anti-prion activity found in beetle grub hemolymph of Trypoxylus dichotomus septentrionalis

No remedies for prion disease have been established, and the conversion of normal to abnormal prion protein, a key event in prion disease, is still unclear. Here we found that substances in beetle grub hemolymph, after they were browned by aging for a month or heating for hours, reduced abnormal prion protein (PrP) levels in RML prion-infected cells. Active anti-prion components in the hemolymph were resistant to protease treatment and had molecular weights larger than 100 kDa. Aminoguanidine treatment of the hemolymph abolished its anti-prion activity, suggesting that Maillard reaction products are enrolled in the activity against the RML prion. However, levels of abnormal PrP in RML prion-infected cells were not decreased by incubation with the Maillard reaction products formed by amino acids or bovine serum albumin. The anti-prion components in the hemolymph modified neither cellular or cell-surface PrP levels nor lipid raft or autophagosome levels. The anti-prion activity was not observed in cells infected with 22 L prion or Fukuoka-1 prion, suggesting the anti-prion action is prion strain-dependent. Although the active components of the hemolymph need to be further evaluated, the present findings imply that certain specific chemical structures in the hemolymph, but not chemical structures common to all Maillard reaction products, are involved in RML prion formation or turnover, without modifying normal PrP expression. The anti-prion components in the hemolymph are a new tool for elucidating strain-dependent prion biology.     

Extra-weak chemiluminescence of drugs. XII. Effect of the molar ratio of amino acid to sugar on extra-weak chemiluminescence in the Maillard reaction

The extra-weak chemiluminescence in the Maillard reaction caused by the reaction between L -lysine and D -arabinose was measured, and a linear relationship was found between the chemiluminescence and the amount of L -lysine added. After a 1-hour reaction equimolar amounts of D -arabinose and L -lysine were consumed regardless of the initial concentration of D -arabinose. The chemiluminescence of the Maillard reaction originates from Maillard reaction products formed by the equimolar reaction between sugar and amino acid and depends on the concentration of amino acid.