Fumitaka Hayase

METABOLISM OF 3-DEOXYGLUCOSONE, AN INTERMEDIATE COMPOUND IN THE MAILLARD REACTION, ADMINISTERED ORALLY OR INTRAVENOUSLY TO RATS

The Amadori rearrangement compound, the product in the early step of the Maillard reaction of proteins with glucose, is known to be degraded into 3-deoxyglucosone (3DG), a 2-oxoaldehyde. In order to elucidate the metabolic pathway of 3DG, [14C]3DG was synthesized from [14C]-glucose and administered to rats orally and intravenously. 2 h after oral administration of [14C]3DG, the percentages of radioactivity (RaI%) in stomach, small intestine and urine were 3.9, 60 and 6.4%, respectively, while RaI% in liver, kidney, spleen, blood and CO2 were less than 0.5%. The absorption rate of 3DG was obviously lower in comparison with that of glucose. 3 h after intravenous administration of [14C]3DG, the RaI% in urine was 72% and those in liver, kidney, spleen, blood and CO2 were less than 1%. It therefore appeared that the absorbed 3DG was not biologically utilized by the rats, but was rapidly excreted in the urine. Some metabolites of [14C]3DG were detected in urine by TLC-autoradiography. The main metabolite was purified and identified as 3-deoxyfructose by FD-MS and 13C-NMR spectroscopy, indicating that the aldehyde group of 3DG was reduced to an alcohol.

Scavenging of Active Oxygen Species by Glycated Proteins

Scavenging of active oxygen species by glycated proteins was investigated. Glycated proteins were prepared from bovine serum albumin (BSA), insulin, and lysozyme incubated with glucose. Glycated BSA at concentration of 0.5% scavenged 34% of hydroxyl radicals by ESR experiments using DMPO as a spin-trapping reagent. The ability to scavenge hydroxyl radicals by glycated BSA was higher than that by BSA. Hydrogen peroxides also were largely scavenged with an increase in the concentration of glycated proteins. However, the ability to scavenge superoxides by glycated BSA was lower than that by BSA because glycated proteins produced superoxides. Experiments using model compounds such as Amadori compound and caproyl pyrraline suggested that the scavenging ability of glycated proteins against hydroxyl radicals depends on Maillard reaction products in the advanced stage, while the ability against hydrogen peroxides is dependent upon Maillard reaction products in the early stage and brown pigments.

Desmutagenic effect of α-dicarbonyl and α-hydroxycarbonyl compounds against mutagenic heterocyclic amines

Abstract The desmutagenic effects of α-hydroxycarbonyl compounds, such as glyceraldehyde, glycolaldehyde, dihydroxyacetone, furtural, 5-hydroxymethylfurfural, maltol, acetol and acetoin and α-dicarbonyl compounds, such as diacetyl, glyoxal, methyl glyoxal and 2,3-pentanedione were investigated against the mutagenic heterocyclic amines, such as Trp-P-1, Trp-P-2, Glu-P-2 and IQ. Most of the carbonyl compounds suppressed the mutagenicity of heterocyclic amines for S. typhimurium TA98, α-dicarbonyl compounds showing a higher desmutagenic effect than α-hydroxycarbonyl compounds. Among the α-hydroxycarbonyl compounds, glyceraldehyde, glycolaldehyde and dihydroxyacetone showed more effective desmutagenicity, and diacetyl among the α-dicarbonyl compounds had the highest desmutagenic effect. These carbonyl compounds alone also showed mutagenecity to S. typhimurium TA100 without S9 mix. The reaction of carbonyl compounds with mutagenic heterocyclic amines also eliminated the mutagenicity of the former for S. typhimurium TA100.

Changes of volatile components of tomato fruits during ripening

Abstract Volatile components obtained by simultaneous steam distillation-extraction from two varieties of tomato fruits at various ripening stages and their artificially ripened tomato fruits were analyzed by GC and GC-MS using a glass capillary column. One hundred and thirty compounds were identified. Of these, quantitative changes in the major thirty-six compounds were investigated. Hexanal, trans -2-hexenal, 2- iso -butylthiazole, 2-methyl-2-hepten-6-one, geranylacetone and farnesylacetone, which were estimated to be important volatile components of fresh tomato aroma by the GC-Sniff method, increased with natural and artificial ripening. However, many volatile components showed complicated changes in the case of artificially ripened tomato fruits.

Desmutagenicity of Melanoidins against Various Kinds of Mutagens and Activated Mutagens.

The desmutagenic activities of low-molecular weight melanoidins (LM-MEL, MW 500-1000) and nondialyzable melanoidins (ND-MEL, MW above 1000) prepared from a glucose-glycine reaction system were examined by Ames test on such mutagens/carcinogens as nitro or amino compounds of aromatics or heterocycles, azo compounds, nitroso compounds, and epoxides. ND-MEL and LM-MEL exhibited a desmutagenic activity of 25-75% against mutagenic aromatic or heterocyclic compounds such as aflatoxin B1, B[α]P, 2-aminofluorene, 4-aminobiphenyl, and 2-aminonaphthalene, as well as heterocyclic amines, using S. typhimurium TA98 in the presence of S9 mix. In the case of using S. typhimurium TA100 in the absence of S9 mix, ND-MEL and LM-MEL showed a desmutagenic activity of 20-50% against 2-nitrofluorene, 4NQO and 2-nitronaphthalene. The strong desmutagenic activity of MEL from various kinds of amino acids, peptides, or egg albumin hydrolyzates with glucose was also observed against Trp-P-1. Furthermore, MEL had marked desmutagenic activity against the Trp-P-1 activated by S9 mix and synthetic N-OH-Trp-P-2.

Chemical changes in casein heated with and without d-glucose in the powdered state or in an aqueous solution

Abstract Chemical changes in casein, heated either in the presence or the absence of d -glucose at 50 or 75°C in a powdered state at 75% relative humidity (RH), or in an aqueous solution, were investigated. During heating, colour development, the formation of polymerised products and severe decomposition of amino acid residues occurred. In the powder reaction system, mainly basic amino acids decomposed whereas, in the solution system, all amino acids were uniformly decomposed. In addition, small amounts of free amino acids and low molecular weight peptides (below MW 500) were detected, these amounts being greater in the solution system, suggesting that non-enzymic cleavage of peptide linkage occurred. These changes were observed both in the absence and in the presence of glucose but glucose promoted such changes.

Aldose Reductase from Porcine Liver Metabolizing 3-Deoxyglucosone, a Maillard Reaction Intermediate.

An enzyme which catalyzes the NADPH-dependent reduction of 3-deoxyglucosone (3DG) was isolated and purified from porcine liver by ammonium sulfate fractionation, and DEAE-cellulose, hydroxyapatite, Sephadex G-100, Blue Sepharose CL-6B, and Sephadex G-100 column chromatographies. The pH for optimum enzyme activity was 6.5. 3DG was a good substrate, and glucose and fructose could also be reduced at a significant rate. The Km values for 3DG, methylglyoxal and glyceraldehyde were 2.5, 1.9, and 4.9 mM, respectively. The molecular mass of the enzyme was estimated to be 67, 000, and the enzyme is proposed to be a dimer composed of identical subunits. The activity of the enzyme was completely inhibited by p-chloromercuribenzoate, and the enzyme is estimated to be an aldose reductase.

Enzymatic metabolism of 3-deoxyglucosone, a Maillard intermediate

SummaryIn order to verify the formation of endogenous 3-deoxyglucosone (3-DG), an intermediate compound in the Maillard reaction, we tried to detect 3-deoxyfructose (3-DF) which is main metabolite of 3-DG. Endogenous 3-DF was detected in the urine of normal and diabetic rats by the oral administration of 3-DG-free feed. Metabolizing activities of crude extracts prepared from porcine organs were examined using methylglyoxal (MG) and 3-DG as substrates. NAD- or NADP-dependent 2-oxoaldehyde dehydrogenase activity was detected in liver, kidney, small intestine and lung. On the other hand, NADH- or NADPH-dependent 2-oxoaldehyde reductase activity was detected in all porcine organs in which liver and kidney contained higher activity of NADPH-dependent enzyme than the other organs. The reductase which catalyzes the reduction of 3-DG to 3-DF and MG to acetol, was purified and characterized from porcine kidney. The enzyme was the same to NADPH-dependent-2-oxoaldehyde reductase from porcine liver, which is speculated to prevent the advanced stage of the Maillard reaction as a self-defense enzyme.

Studies on Roasting Changes of Proteins Part I:Changes of Casein and Lysozyme during Roasting

Changes of casein and lysozyme during roasting at various times and temperatures 100 ~ 300°C), especially those in amino acid composition and formation of some nonvolatile degradation products, were investigated.Tryptophan, methionine, basic amino acids and β-hydroxy amino acids were easily decomposed as compared with acidic amino acids and other neutral amino acids in casein and Iysozyme. In hot water extract of roasted casein were detected some free amino acids, peptides, organic acids such as α-ketoglutaric, tartaric and malic acids, and indole. It is considered that free amino acids are produced mainly through ionic cleavage of peptide bond with the water bound within casein.