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At least 19 recordsLinked to original sources
PubMed1979

Carbon-13-enriched carbohydrates: preparation of triose, tetrose, and pentose phosphates.

Three-, four-, and five-carbon aldononitrile phosphates were prepared, purified, and catalyticlly reduced with palladium--barium sulfate (5%) to the corresponding aldose phosphates in high yields at pH 1.7 +/- 0.1 and atmopsheric pressure. DL-Glyceraldehyde 3-phosphate and the tetrose 4-phosphates were prepared with carbon-13 enrichment at C-1, while the pentose 5-phosphates were prepared with enrichment at C-1 and C-2. Preparations of glycolaldehyde phosphate and d-glyceraldehyde 3-phosphate by lead tetra-acetate oxidation of glycerol phosphate and fructose 6-phosphate, respectively, are described. The proportions of cyclic hemiacetals and linear gem-diol forms of the two- to five-carbon aldose phosphates in aqueous solution are reported. Carbon-13 chemical shifts and carbon--phosphorus and carbon--hydrogen coupling constants for the furanose phosphate ring and linear gem-diol phosphates are reported and discussed. d-[2(-13)C]Ribulose 1,5-bisphosphate and L-[3,4(-13)C]sorbose 1,6-bisphosphate were prepared enzymatically from D-[2(-13)C]ribose 5-phosphate and dl-[1(-13)C]glyceraldehyde 3-phosphate, respectively.

Carbohydrate Epimerases↗
PubMed1975

Studies on D-tetrose metabolism. VI. Crystallization and some properties of D-erythrulose reducatase from beef liver.

D-Erythrulose reductase of beef liver was crystallized from ammonium sulfate solution at pH 8.17. The crystals are needle-shaped. The enzyme protein contains 851 amino acid residues per mole of the enzyme: Lys28, His11, Arg52, Asp79, Thr58, Ser56, Glu68, Pro20, Gly80, Ala107, Val112, Met24, Ile31, Leu88, Tyr7, Phe22, Trp4, and Cys4. The enzyme is inactivated by exposure to temperatures below 12degrees. The inactivation is accelerated by increasing the salt concentration and decreasing the enzyme concentration. The pH of the medium also has a pronounced effect, the maximum stability of the enzyme is obtained at pH 8.5. NADP+ protected the enzyme from cold inactivation at all stages of the process and also afforded protection against inactivation by heat and pH. The cold inactivation of the enzyme is accompanied by dissociation of the enzyme protein to subunits.

Alcohol Oxidoreductases↗
PubMed1980

Studies on D-tetrose metabolism. Crystallization and properties of D-erythrulose reductase from chicken liver.

D-Erythrulose reductase from chicken liver has been purified to homogeneity as judged by acrylamide gel electrophoresis and ultracentrifugation. The overall purification of the enzyme was 164-fold from a crude extract. The enzyme was crystallized from ammonium sulfate solution at pH 7.0 to give hexagonal plates. The molecular weight determined by sedimentation equilibrium analysis was 94,600 and that by SDS-polyacrylamide gel electrophoresis was 22,400, which suggests a tetrameric structure for the native enzyme. The enzyme was found to contain up to 3 molecules of NADP+ per enzyme; this high amount of NADP+ resulted in a higher absorption at 260 nm than at 280 nm. The extinction coefficient of the enzyme at 290 nm was found to be 4.0. The contents of various amino acids were very similar to those of the beef liver enzyme formerly crystallized in our laboratory. The isoelectric point of the enzyme determined by Ampholine isoelectric focusing was pH 6.43. The enzyme was shown to catalyze the reduction of D-erythrulose to D-threitol with the concomitant oxidation of NAD(P)H to NAD(P)+, and was highly specific to D-erythrulose with an apparent Km of 0.38 mM. NADH was less effective than NADPH and the Km's for NADH and NADPH were 67 micrometers and 7.9 micrometers, respectively. D-Threitol was slightly oxidized by the enzyme with either NADP+ or NAD+ as a cofactor at pH's 7.5 and 9.0.

Amino Acids↗
PubMed1997

[Inhibitory effects of two oligosaccharides on murine melanoma experimental metastasis].

OBJECTIVE: To observe the effects of a chemically synthesized tetrose and a natural yeast mannan on mouse melanoma experimental liver metastasis. METHODS: After treated with 4 mg tetrose (tetrose group) or 4 mg mannan (mannan group) for 30 minutes at 37 degrees C, 0.5 ml 1 x 10(6)B16-MBK melanoma cells were injected intraspleen. 55 days later, melanoma metastasis nodes in the surfaces of the liver and other organs as well as mouse survival time were observed. RESULTS: Of 6 mice in control (B16 cell+PBS), 4 died naturally within 55 days, 2 were dissected in the 55th day. All of the 6 mice had metastases in the livers, the total number of the melanoma nodes on each liver surface ranged from 2 to 30, with the largest one fused to the whole liver. One mouse had a neoplasm in the remnant site of injection, 3 had metastases in lungs, while of the 6 mice in the tetrose group, one died on the 50th day on injection. In mannan group, all of the 6 mice survived and no metastasis was seen except the largest diameter of < 1 mm of 2 liver nodes in one mouse. Neither tetrose nor mannan group had metastasis of the liver, and the weights of liver in the two groups were significantly lower than in the control. CONCLUSION: Both tetrose and mannan had the effects in blocking melanoma experimental liver metastasis, inhibiting transmigration of the liver, and prolonging the survival time of the mouse.

Animals↗
PubMed1998

Inhibitory effects of two oligosaccharides on murine melanoma experimental liver metastasis.

AIM:To observe the effects of a chemically synthesized tetrose and a natural yeast mannan on experimental liver metastasis of mouse melanoma.METHODS: After treated with 4mg tetrose (tetrose group) or 4mg mannan (mannan group) for 30 minutes at 37&mgr;,0.5ml 1 10(6) B16-MBK melanoma cells were injected into the spleen of mice.Fifty-five days later, melanoma metastatic nodes on the surface of the liver and in other organs as well as mouse survival time were observed.RESULTS: Of the 6 mice in control (B16 cell+PBS) group, 4 died naturally within 55 days, and 2 were killed on the 55th day.All of the 6 mice had metastases in livers, the total number of the melanoma nodes on each liver surface ranged from 2 to 30, with the largest one merging into the whole liver. One mouse had a neoplasm in the remnant site of injection, and 3 had metastases in lungs.In contrast, of the 6 mice in tetrose group, only one died on the 50th day after injection, with 3 metastases in the liver, the largest being 10mm in diameter, the other 5 mice survived until being dissected on the 55th day after injection and had no liver metastasis,but 3 of them had neoplasms in their remnant sites of injection.In mannan group,all of the 6 mice survived and no metastasis was seen except for 2 liver nodes in one mouse with the largest diameter of 1mm.Neither tetrose nor mannan group had metastasis out of the liver, and the weight of liver in the two groups was significantly lower than those in the control group.CONCLUSION:Both tetrose and mannan had the effects of preventing melanoma cells from experimental metastasis to and out of the liver, and prolonging the survival time of the mouse.

Journal Article↗
PubMed1995

Formation of reactive intermediates from Amadori compounds under physiological conditions.

The Maillard or browning reaction between reducing sugars and proteins contributes to the chemical aging of tissue proteins in vivo and to the accelerated aging of proteins in diabetes. To identify reactive carbohydrate intermediates formed in the Maillard reaction under physiological conditions, we studied the decomposition of the model Amadori compound, N alpha-formyl-N epsilon-fructoselysine (fFL) and of Amadori compounds on glycated collagen at pH 7.4 and 37 degrees C. Because of effects of buffer and oxidative conditions on the decomposition of Amadori compounds, the kinetics and products of decomposition were studied in varying phosphate concentrations and in N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (Hepes) buffer under both aerobic and anaerobic conditions. The half-life of fFL was significantly shorter in phosphate, compared to Hepes buffer, and under aerobic, compared to anaerobic, conditions. The decomposition of both fFL and Amadori adducts on glycated collagen was accelerated by increasing the phosphate concentration and/or pH. Glucose and mannose were identified as major products formed by reversal of the Amadori rearrangement, along with tetroses, pentoses, and 3-deoxyglucosone, formed by reverse aldol, rearrangement, and hydrolysis reactions. The tetrose and pentose products included both aldose and ketose sugars. These same products were also formed in similar yields on decomposition of Amadori adducts on glycated collagen in vitro. The spontaneous decomposition of Amadori compounds to more reactive sugars in vivo, including tetroses, pentoses, and 3-deoxyglucosone, provides a mechanism for generating reactive intermediates under physiological conditions and for propagating damage to protein as a result of glycation of proteins by glucose in vivo.

Aerobiosis↗
PubMed1991

Deoxygenated and alkylated furanoses: Thorpe-Ingold effects on tautomeric equilibria and rates of anomerization.

2-Deoxy-D-glycero-tetrose, 3-deoxy-DL-glycero-tetrose, 3-deoxy-3,3-di-C-methyl-DL-glycero-tetrose, 3-C-methyl-DL-erythrose, 3-C-methyl-DL-threose, 2-deoxy-5-O-methyl-D-erythro-pentose and 3-deoxy-5-O-methyl-D-erythro-pentose have been prepared, in some cases with 13C-substitution at the anomeric carbon, and characterized by 1H-(300 and 620 MHz) and 13C-n.m.r. (75 MHz) spectroscopy. The proportions of cyclic (alpha and beta furanoses) and acyclic (aldehyde and hydrate) forms were determined in aqueous (2H2O) solution, and ring-opening (kopen) and ring-closing (kclose) rate constants were measured by 1H and 13C saturation-transfer n.m.r. spectroscopy at p2H 5.0 (acetate buffer) and 60 degrees. The degree of furanose ring substitution was found to significantly affect both the thermodynamics and kinetics of furanose anomerization. Increased substitution enhances the proportion of cyclic forms in solution by stimulating furanose kclose. In contrast, furanose kopen was less affected by the degree of substitution; however, kinetic studies of 2-deoxyfuranose anomerization implicate furanose ring conformation as a potential determinant of kopen.

Alkylation↗
PubMed1994

Ascorbic acid glycation: the reactions of L-threose in lens tissue.

L-Threose is a significant degradation product of ascorbic acid at pH 7.0 in the presence of oxygen. When compared to several other ascorbate-derived degradation products, it had the greatest ability to glycate and crosslink lens proteins in vitro. To determine whether L-threose was formed in the lens, the sugars in a TCA-soluble extract from human lenses were reduced to polyols with NaBH4, acetylated and analysed by gas-liquid chromatography. The threitol levels measured were 3.4 +/- 0.8 micrograms per lens (n = 4). GC-MS measurements made after reduction with NaBD4 indicated that threitol, but little or no threose, was originally present in the human lens. Rat lenses were incubated with [1-13C]D-threose for 24 hr, and considerable D-threitol formation was seen by NMR spectroscopy. Analysis of the lenses after medium removal showed that only [1-13C]threitol was present within the lenses indicating a rapid reduction of threose within the lens, presumably by aldose reductase. Assays with human recombinant aldose reductase and with human lens cortical and nuclear extracts all exhibited sorbinil-inhibitable aldose reductase activity with L-threose as substrate. This was confirmed by incubating a preparation of [1-14C]L-tetrose (a mixture of 40% L-threose and 45% L-erythrose) with both the pure aldose reductase and crude lens extracts followed by the subsequent identification of the [1-14C]L-threitol formed by thin layer chromatography. L-Threose degrades very slowly in 0.1 M phosphate buffer at pH 7.0, but the addition of a four-fold excess of N alpha-acetyl-L-lysine accelerated the rate of disappearance of threose 30-fold, indicating a rapid glycation reaction. When [1-14C]L-tetrose was incubated with a complete bovine lens homogenate, a linear incorporation into protein was observed over a 24 hr period. Increasing levels of lens extract exhibited increasing incorporation into protein. These data confirm a rapid reactivity of L-threose with lens protein and argue that glycation would occur in vivo in spite of the presence of aldose reductase.

Aldehyde Reductase↗
PubMed1977

Biosynthesis of the dimethylbenzene moiety of riboflavin and dimethylbenzimidazole: evidence for the involvement of C-1 of a pentose as a precursor.

The relative incorporations of specially labeled pyruvate, lactate, erythritol, D-erythrose, D-ribose, and D-glucose precursors into the dimethylbenzene carbon atoms of the 5,6-dimethylbenzimidazole unit of vitamin B12 by Propionibacterium shermanii have been determined. The incorporation data provide information regarding the putative four-carbon biosynthetic unit which is involved in the formation of 6,7-dimethyl-8-ribityllumazine and which is the source of the eight dimethylbenzene carbon atoms of both 5,6-dimethylbenzimidazole and riboflavin. The relative incorporations of the labeled lactate and pyruvate precursors are not consistent with either acetoin or 2,3-butanedione functioning as the four-carbon biosynthetic unit. The relative incorporations of the labeled hexose, pentose, and tetrose precursors indicate that the observed incorporation of C-1 of the pentose into the dimethylbenzene carbon atoms does not involve metabolism to a tetrose intermediate, but occurs more directly. It is concluded that the C-1 position of a pentose precursor is involved in the formation of the putative four-carbon biosynthetic unit.

Benzimidazoles↗