muramidase and 3-deoxyglucosone

The nonenzymatic reaction between reducing sugars and proteins, known as the Maillard reaction, has received increased recognition from nutritional science and medical research. The development of new analytical techniques for the detection of protein-bound Maillard products is therefore crucial. In this study, we applied peptide mapping by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry to investigate the formation of structurally specific Maillard products on glycated lysozyme (AGE-lysozyme), produced upon incubation with D-glucose. In parallel, we synthesized N(epsilon)-(carboxymethyl)lysine-modified lysozyme (CML-lysozyme) and N(epsilon)-(carboxyethyl)lysine-modified lysozyme, two well-described glycation products, as model substances. 3-Deoxyglucosone-modified lysozyme and methylglyoxal-modified lysozyme were prepared as examples of glycation products incubated with dicarbonyl compounds. We were able to detect specific modifications on AGE-lysozyme, which were assigned to CML, imidazolone A, and the Amadori product.

Topics: Deoxyglucose; Electrophoresis, Polyacrylamide Gel; Enzyme-Linked Immunosorbent Assay; Glucose; Glycoproteins; Glycosylation; Lysine; Maillard Reaction; Muramidase; Peptide Mapping; Pyruvaldehyde; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Structure-Activity Relationship

3-Deoxyglucosone (3-DG) has been identified as an intermediate of the Maillard reaction in vitro. We measured serum 3-DG levels using gas chromatography/mass spectrometry and found a marked elevation in serum 3-DG levels in uremic patients compared with healthy subjects. The uremic patients with diabetes showed significantly higher serum concentrations of 3-DG than those without diabetes. 3-DG was demonstrated to be a potent protein-cross-linking agent in the reaction with lysozyme, leading to browning, fluorescence formation and polymerization of the protein by formation of advanced glycation end products (AGE). The increase in serum 3-DG levels in the uremic patients suggests that 3-DG may be responsible for the development of uremic complications by promoting the formation of AGE.

Topics: Adult; Aged; Blood Proteins; Cross-Linking Reagents; Deoxyglucose; Diabetic Nephropathies; Female; Gas Chromatography-Mass Spectrometry; Humans; In Vitro Techniques; Maillard Reaction; Male; Middle Aged; Muramidase; Uremia

We investigated the effect of exogenously applied 3-deoxyglucosone, a major carbonyl intermediate, on the Maillard reaction. The fluorescence intensity of the product of the reaction of bovine serum albumin with 3-deoxyglucosone was higher than that with an equivalent amount of glucose. Similarly the rate of polymerization of lysozyme in the presence of 3-deoxyglucosone was also greater than with glucose, and collagen incubated with 3-deoxyglucosone was less digestible than collagen incubated with glucose. By contrast, aminoguanidine inhibited an increase in fluorescence of the Maillard compounds and the polymerization of protein, both of which were stimulated by 3-deoxyglucosone. These results suggest that 3-deoxyglucosone accelerates the advanced stage of the Maillard reaction and that aminoguanidine acts on 3-deoxyglucosone to inhibit its action in the advanced stage of the Maillard reaction.

Topics: Collagen; Deoxy Sugars; Deoxyglucose; Glucose; Glycosylation; Guanidines; Maillard Reaction; Microbial Collagenase; Muramidase; Polymers; Serum Albumin, Bovine; Spectrometry, Fluorescence

The Maillard reactions between proteins and glucose or fructose, in 0.2M phosphate buffer (pH 7.4) at 37 degrees C, were investigated and the following results were obtained: 1) 3-deoxyglucosone (3DG) is formed as the major carbonyl intermediate; 2) fructose has a higher reactivity than glucose and 3DG is formed also from fructose without involvement of amino groups; 3) 3DG is a crosslinker responsible for polymerization of proteins; 4) 3DG is involved in the formation of a fluorescent advanced-stage product named "Peak L1" in vitro and in vivo.

Topics: Biopolymers; Carbohydrate Metabolism; Chemical Phenomena; Chemistry; Deoxy Sugars; Deoxyglucose; Fructose; Glucose; Maillard Reaction; Muramidase; Proteins