Protein and low molecular mass thiols as targets and inhibitors of glycation reactions

TY - JOUR

T1 - Protein and low molecular mass thiols as targets and inhibitors of glycation reactions

AU - Zeng, Jingmin

AU - Davies, Michael Jonathan

PY - 2006/12

Y1 - 2006/12

N2 - Protein glycation has been implicated in the aging process as well as the complications of diabetes (retinopathy, neuropathy, nephropathy, and atherosclerosis). The nitrogen substituents of Lys, Arg, and His residues and the N-terminus of proteins are known to be readily glycated. As the thiol group of Cys is a powerful nucleophile, we hypothesized that Cys residues should also be targets of glycation and that low molecular mass thiols may act as protective agents. In this study the role of thiol glycation, induced by dicarbonyls, in protein cross-link formation and damage prevention is examined. It is shown that incubation of creatine kinase with glyoxal results in protein cross-link formation, with this occurring concurrently with loss of thiol groups, enzyme inactivation, and formation of S-carboxymethylcysteine, a product of glyoxal adduction to Cys residues. Cross-links have also been detected between N-acetylcysteine and the Lys-rich protein histone H1, demonstrating the formation of thiol-glyoxal-amine cross-links. Mass spectrometry has been used to characterize some of these cross-links as 2-(alkylthio)acetamides. A range of low molecular mass thiols have been shown to inhibit dicarbonyl adduction to, and cross-linking of, the thiol-free protein lysozyme, consistent with these thiols being alternative (sacrificial) targets of glycation. Some of these thiols are more efficient modulators of glycation than established glycation inhibitors such as aminoguanidine. These data demonstrate that thiols are facile targets of glycation and that low molecular mass thiols are potent glycation inhibitors. These data may aid the design of therapeutic agents for the treatment of the complications of diabetes.

AB - Protein glycation has been implicated in the aging process as well as the complications of diabetes (retinopathy, neuropathy, nephropathy, and atherosclerosis). The nitrogen substituents of Lys, Arg, and His residues and the N-terminus of proteins are known to be readily glycated. As the thiol group of Cys is a powerful nucleophile, we hypothesized that Cys residues should also be targets of glycation and that low molecular mass thiols may act as protective agents. In this study the role of thiol glycation, induced by dicarbonyls, in protein cross-link formation and damage prevention is examined. It is shown that incubation of creatine kinase with glyoxal results in protein cross-link formation, with this occurring concurrently with loss of thiol groups, enzyme inactivation, and formation of S-carboxymethylcysteine, a product of glyoxal adduction to Cys residues. Cross-links have also been detected between N-acetylcysteine and the Lys-rich protein histone H1, demonstrating the formation of thiol-glyoxal-amine cross-links. Mass spectrometry has been used to characterize some of these cross-links as 2-(alkylthio)acetamides. A range of low molecular mass thiols have been shown to inhibit dicarbonyl adduction to, and cross-linking of, the thiol-free protein lysozyme, consistent with these thiols being alternative (sacrificial) targets of glycation. Some of these thiols are more efficient modulators of glycation than established glycation inhibitors such as aminoguanidine. These data demonstrate that thiols are facile targets of glycation and that low molecular mass thiols are potent glycation inhibitors. These data may aid the design of therapeutic agents for the treatment of the complications of diabetes.

KW - Amino Acids

KW - Creatine Kinase

KW - Cross-Linking Reagents

KW - Electrophoresis, Polyacrylamide Gel

KW - Glycosylation

KW - Glyoxal

KW - Molecular Weight

KW - Muramidase

KW - Proteins

KW - Spectrometry, Mass, Electrospray Ionization

KW - Sulfhydryl Compounds

U2 - 10.1021/tx0602158

DO - 10.1021/tx0602158

M3 - Journal article

C2 - 17173381

SN - 0893-228X

VL - 19

SP - 1668

EP - 1676

JO - Chemical Research in Toxicology

JF - Chemical Research in Toxicology

IS - 12

ER -