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PubMedDate not supplied

Analysis of CHO cells metabolic redistribution in a glutamate-based defined medium in continuous culture.

The effect of glutamine replacement by glutamate and the balance between glutamate and glucose metabolism on the redistribution of t-PA-producing recombinant CHO cells metabolism is studied in a series of glucose shift down and shift up experiments in continuous culture. These experiments reveal the existence of multiple steady states, and experimental data are used to perform metabolic flux analysis to gain a better insight into cellular metabolism and its redistribution. Regulation of glucose feed rate promotes a higher efficiency of glucose and nitrogen source utilization, with lower production of metabolic byproducts, but this reduces t-PA specific production rate. This reduction under glucose limitation can be attributed to the fact that the cells are forced to efficiently utilize the carbon and energy source for growth, impairing the production of dispensable metabolites. It is, therefore, the combination of growth rate and carbon and energy source availability that determines the level of t-PA production in continuous culture.

Adenosine Triphosphate↗
PubMedDate not supplied

Reductive microbial dechlorination of indigenous polychlorinated biphenyls in soil using a sediment-free inoculum.

In laboratory experiments, unagitated soil slurry bioreactors inoculated with micro-organisms extracted from polychlorinated biphenyl-contaminated (PCBs) sediments from the Hudson River were used to anaerobically dechlorinate PCBs. The onset of dechlorination activity was accelerated by the addition of certain organic acids (pyruvate and maleate) and single congeners (2,3,6-trichlorobiphenyl). Dechlorination was observed under several working conditions after 19 weeks of incubation with PCB-contaminated soil and nutrient solution. Best results showed a drop in average chlorine content from 4.3 to 3.6 chlorines per biphenyl due to a loss of m-chlorines. Soil used for these experiments was obtained from a PCB-contaminated (weathered Aroclor 1248) site at an electric power substation. Dechlorination was observed with no sediment particles or other matrix being added.

Anaerobiosis↗
PubMed2001

Biosynthesis of vitamin B(6) in yeast: incorporation pattern of glucose.

Two yeasts, Saccharomyces cerevisiae ATCC 7752 and Candida utilis ATCC 9256, were incubated in the presence of variously multiply (13)C-labeled samples of D-glucose. The (13)C incorporation pattern within pyridoxamine dihydrochloride, established by (13)C NMR spectroscopy, differed from that which had previously been found within pyridoxine, isolated from Escherichia coli. Thus, the origin of the carbon skeleton of vitamin B(6) in yeast differs substantially from its origin in E. coli. In particular, in yeast the distribution of (13)C within the C(5) chain C-2',2,3,4,4' of pyridoxamine corresponds to the distribution of (13)C within the C(5) chain C-1,2,3,4,5 of the ribose component of cytidine. It follows that the C(5) chains of pyridoxamine and of ribose originate from a common glucose-derived pentulose or pentose intermediate. By contrast, in E. coli the C(5) chain of pyridoxine is derived from 1-deoxy-D-xylulose 5-phosphate which, in turn, originates by condensation of pyruvic acid with glyceraldehyde 3-phosphate.

Candida↗
PubMed2002

A potent polymer/pyridoxamine enzyme mimic.

An enzyme mimic consisting of pyridoxamines covalently linked to polyethyleneimine carrying long-chain alkyl groups converts pyruvic acid to dl-alanine with as much as an 8000-fold acceleration relative to the reaction with simple pyridoxamine at the same pyridoxamine concentration. The acceleration by polymer is a strong function of the length of the alkyl chains that are appended. The polymer furnishes acid and base groups to catalyze the proton transfers that are involved in transamination.

Kinetics↗
PubMed2003

Vitisin A content in Chilean wines from Vitis vinifera Cv. Cabernet Sauvignon and contribution to the color of aged red wines.

Vitisin A was prepared from malvidin 3-glucoside and pyruvic acid in model wine medium, isolated by countercurrent chromatography, and purified by preparative high-performance liquid chromatography (HPLC). The synthesized compound was used as a reference standard to quantify vitisin A in Chilean wines from Vitis vinifera cv. Cabernet Sauvignon, including a vertical row of wines from the same vineyard over 16 years. Maximum vitisin A content was reached within the first year of storage. Importantly, up to half of the initial amount of vitisin A in young wines was still present in 15 year old wines. Although vitisin A was found to be much more stable as compared to other monomeric C-4 underivatized anthocyanins, it also slowly degrades after reaching its peak concentration. The "color activity concept" was applied to vitisin A, malvidin 3-glucoside, malvidin 3-(6' '-acetylglucoside), and polymeric pigments isolated by countercurrent chromatography in order to estimate their contribution toward the overall color expression of wines. It was found that vitisin A is only a minor contributor to the visually perceived color of aged red wines (color contribution approximately 5%). The major contributor is the polymeric fraction (color contribution approximately 70-90%).

Benzofurans↗
PubMed2004

Antioxidant and cellular activities of anthocyanins and their corresponding vitisins A--studies in platelets, monocytes, and human endothelial cells.

During red wine aging, there is a loss of anthocyanins and the formation of various other pigments, so-called vitisins A, which are formed through the chemical interaction of the original anthocyanins with pyruvic acid. The objective of this study was to investigate the antioxidant activities of the most abundant anthocyanins present in red wine (glycosides of delphinidin, petunidin, and malvidin) and their corresponding vitisins A. Anthocyanins exhibited a higher iron reducing as well as 2,2'-azinobis (3-ethyl-benzothiazoline-6-sulfonate) and peroxyl radical scavenging activity than their corresponding vitisins A. Delphinidin showed the highest antioxidant effect of the tested compounds in all of the assays used. Furthermore, we studied the effect of anthocyanins and vitisins A on platelet aggregation and monocyte and endothelial function. Anthocyanins and vitisins did not affect nitric oxide production and tumor necrosis factor-alpha (TNF-alpha) secretion in lipopolysaccharide plus interferon-gamma-activated macrophages. Furthermore, anthocyanins and vitisins did not change collagen-induced platelet aggregation in vitro. However, anthocyanins and to a lesser extent vitisins exhibited protective effects against TNF-alpha-induced monocyte chemoattractant protein production in primary human endothelial cells.

Anthocyanins↗
PubMed2005

Antioxidant properties of prepared blueberry (Vaccinium myrtillus) extracts.

A blueberry extract (A) and two anthocyanin-derived extracts (B and C) were prepared. The contents of polyphenols, flavonoids, anthocyanins, and anthocyanin-derived pigments of the extracts were determined for the first time. The pigment profile of blueberry extract A corresponded to 15 anthocyanins, whereas extract B was mainly composed of anthocyanin-pyruvic acid adducts of the blueberry original anthocyanins and extract C was mainly composed of the respective vinylpyranoanthocyanin-catechins (portisins). The extracts' abilities to inhibit lipid peroxidation, induced by 2,2'-azobis(2-methyl-propanimidamide) dihydrochloride in a liposomal membrane system were examined. The antioxidant capacities of the extracts were evaluated through monitoring oxygen consumption and by measuring the formation of conjugated dienes. All of the extracts provided protection of membranes against peroxyl radicals by increasing the induction time of oxidation. This effect increased with the polyphenol content and with the structural complexity of the anthocyanin-derived pigments of the extracts. The pigments present in extract C seemed to induce a higher protection of the liposome membranes toward oxidation. In addition, the antiradical properties and the reducing power of the extracts were determined by using DPPH and FRAP methods, respectively. The results from these assays were in agreement with those obtained with the liposome membranes.

Anthocyanins↗
PubMed2000

Formation of sugar-specific reactive intermediates from (13)C-labeled L-serines.

Analysis of the pyrolysis products of [1-(13)C], [2-(13)C], and [3-(13)C]-labeled L-serines has indicated the presence of three initial degradation pathways. Decarboxylation followed by deamination produces aminoethanol and acetaldehyde, respectively; a retro-aldol pathway generates formaldehyde and glycine. Dehydration of L-serine can lead to the formation of pyruvic acid, which eventually can be converted into the amino acid alanine. Formation of alanine and glycine was confirmed due to the detection of 2, 5-diketo-3,6-dimethylpiperazine and cycloglycylalanine. Most of the advanced decomposition products of L-serine can be rationalized on the basis of these initial degradation products. Label incorporation studies have elucidated the origin of carbonyl precursors of methyl- and 2,3-dimethylpyrazines formed in the thermal decomposition mixture of L-serine. Three mechanistic pathways were identified for the formation of carbonyl precursors of methyl- and 2, 3-dimethylpyrazines. The major pathway (70%) for the formation of the precursor of methylpyrazine involved aldol addition of formaldehyde to glycolaldehyde to form glyceraldehyde. On the other hand, the major pathway (60%) for the formation of the precursor of 2,3-dimethylpyrazine involved an aldol condensation of acetaldehyde with glycolaldehyde to form 2,3-butanedione.

Carbon Isotopes↗
PubMed1978

Inhibition of four human serine proteases by substituted benzamidines.

A series of substituted benzamidines has been examined for their inhibitory activity against the human serine proteases--trypsin, thrombin, plasmin, and C1s, a subunit of the first component of complement. The inhibition constants obtained for each enzyme were correlated with physical-chemical properties of the substituent group using the quantitative structure-activity relationship approach. This analysis indicated that plasmin and C1s are very similar in their interactions with substituted benzamidines. The binding of benzamidines in both enzymes was affected by electron donation from the substituent and its hydrophobicity. Thrombin-benzamidine interaction was affected only by the hydrophobicity of the substituent. Trypsin displayed a complex interaction with substituted benzamidines, and interaction was dependent on molar refractivity and molecular weight. Certain substituents deviated significantly from the interactions predicted by the analysis. These compounds, the (m- and p-amidinophenyl)pyruvic acids, when analyzed by computer modeling, suggested that direct interaction between the substituent and the enzyme surface is important in assessing the effect of substituent groups on inhibitory activity.

Amidines↗
PubMed2004

N-vinyl-2-oxazolidinones: efficient chiral dienophiles for the [4 + 2]-based de novo synthesis of new N-2-deoxyglycosides.

Under smooth Eu(fod)(3)-catalyzed conditions, the inverse-electron demand hetero-Diels-Alder reactions between enantiopure N-vinyl-2-oxazolidinones 1a-f and representative beta,gamma-unsaturated alpha-ketoesters proceed with a high degree of endo and facial diastereoselectivity. The elucidation of the stereostructure of these adducts, performed by X-ray analysis or chemical correlation, shows that the endo-selective cycloaddition process is facially controlled in favor of the (2S,4S)-adduct when starting from a (4S)-dienophile or vice versa. The specific interest of the adducts 10a-e, derived from (E)-4-tert-butoxymethylene pyruvic acid methyl ester 9, has been exemplified by the two-step and highly stereoselective transformation of these adducts into the new and valuable N-2-deoxyglycosyl-oxazolidinones 12a-e, isolated in a pure diastereo- and enantiomeric form.

Journal Article↗
PubMed2005

Syntheses of tetrahydrofurobenzofurans and dihydromethanobenzodioxepines from 5-hydroxy-3-methyl-3H-benzofuran-2-one. Rearrangement and ring expansion under reductive conditions on treatment with hydrides.

5-Hydroxy-3-methyl-3H-benzofuran-2-one, 5, easily obtained from pyruvic acid and 1,4-cyclohexanedione, was used as a starting material to prepare (+/-)-5-hydroxy-3a-methyl-2,3,3a,8a-tetrahydro-furo[2,3-b]benzofuran, 10, and (+/-)-7-hydroxy-5-methyl-4,5-dihydro-2,5-methano-1,3-benzodioxepine, 14. Reduced reactivity relative to 5-hydroxy-3-methoxycarbonylmethylene-3-methyl-3H-benzofuran-2-one, 6, was preliminarily studied. Meanwhile, a plausible mechanism with regard to the formation of 10 and 14, which included cyclization, rearrangement, and ring expansion of hemiacetal, 15, is proposed. Specific carbamates of phenols, 10 and 14, have shown impressive inhibitory activities against human acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) ex vivo.

Benzofurans↗
PubMed1997

Prebiotic transamination.

Biological amino acids and alpha keto acids directly condense with decarboxylation and transamination to yield product amino acids. This process is closely related to unusual amino acid decarboxylase enzymes in certain microorganisms and may represent a primordial mode of amino acid metabolism.

Alanine↗
PubMed2001

Optimized labeling of 13CHD2 methyl isotopomers in perdeuterated proteins: potential advantages for 13C relaxation studies of methyl dynamics of larger proteins.

13CHD2 methyl isotopomers are particularly useful to study methyl dynamics in proteins because, as compared with other methyl isotopomers, the 13C relaxation mechanism for this isotopomer is straightforward. However, in the case of proteins, where (omega tau)2 >> 1, the refocused INEPT pulse sequence does not completely suppress unwanted 13CH3 signals. The presence of weak 13CH3 peaks is usually not a serious problem for smaller proteins because there are relatively few methyl signals and they are sharp; however, signal overlap becomes more common as the size of the protein increases. We overcome this problem by preparing a protein using a 98% D2O cell culture medium containing 3-(13)C pyruvic acid, 50-60% deuterated at the 3-position, and 4-(13)C 2-ketobutyric acid, 98% and 62% deuterated at the 3- and 4-positions, respectively. This approach significantly reduces the population of the CH3 isotopomer while optimizing the production of 13CHD2, the isotopomer desired for 13C relaxation measurements. In larger proteins where the deuterium T2 may be too short to measure accurately, we also suggest the alternative measurement of the proton T2 of the 13CH2D methyl isotopomer, because these protons are well-isolated from other protons in these highly deuterated samples.

Carbon Isotopes↗
PubMed1998

Human beta-tryptase is a ring-like tetramer with active sites facing a central pore.

Human tryptase, a mast-cell-specific serine proteinase that may be involved in causing asthma and other allergic and inflammatory disorders, is unique in two respects: it is enzymatically active only as a heparin-stabilized tetramer, and it is resistant to all known endogenous proteinase inhibitors. The 3-A crystal structure of human beta-tryptase in a complex with 4-amidinophenyl pyruvic acid shows four quasi-equivalent monomers arranged in a square flat ring of pseudo 222 symmetry. Each monomer contacts its neighbours at two different interfaces through six loop segments. These loops are located around the active site of beta-tryptase and differ considerably in length and conformation from loops of other trypsin-like proteinases. The four active centres of the tetramer are directed towards an oval central pore, restricting access for macromolecular substrates and enzyme inhibitors. Heparin chains might stabilize the complex by binding to an elongated patch of positively charged residues spanning two adjacent monomers. The nature of this unique tetrameric architecture explains many of tryptase's biochemical properties and provides a basis for the rational design of monofunctional and bifunctional tryptase inhibitors.

Amino Acid Sequence↗
PubMed1980

Hydralazine kinetics in hypertensive patients after intravenous administration.

Previous studies on intravenous hydralazine kinetics have been performed using nonselective analytical techniques that measure not only hydralazine but also certain hydralazine metabolites such as hydralazine pyruvic acid hydrazone (HPH). We studied the time course of hydralazine and HPH in eight hypertensive patients after 0.3 mg/kg intravenous with selective high-pressure liquid chromatographic assays. "Apparent" hydralazine concentrations were also determined using a nonselective gas-liquid chromatographic procedure. Total plasma clearance, CLT[72.9 +/- 4.9 (SEM) ml . min-1 . kg-1], apparent volume of distribution, Vd area (5.83 +/- 0.30 1 . kg-1), steady-state volume of distribution, Vd ss (1.83 +/- 0.17 . kg-1), and terminal half-life, t1/2 (53.7 min, harmonic mean) were independent of acetylator phenotype. The high ClT is compatible with rapid intravascular conversion of hydralazine to HPH and a high hepatic extraction ratio. Peak HPH concentrations occurred 10 to 60 min after dose; mean HPH t1/2 was 239 min. "Apparent" hydralazine concentrations were usually highest in the 2-min plasma sample and declined with a mean t1/2 of 296 min. Reports based on nonselective assay methods have underestimated CLT, Vd ss, and Vd area and have overestimated the t1/2 of hydralazine.

Half-Life↗
PubMed1983

Effect of intravenous dose on hydralazine kinetics after administration.

Six male hypertensive patients, three rapid and three slow acetylators, each received four different intravenous hydralazine doses by constant infusion over 100 sec. Two to four days elapsed between doses. Plasma or whole-blood hydralazine concentrations were measured by HPLC after each dose. There was no influence of acetylator phenotype on hydralazine kinetics after intravenous dosing. There also was no consistent effect of dose size on hydralazine clearance or volume of distribution at doses up to 0.45 mg (2.3 mumol/kg). One subject, who received doses up to 0.6 mg/kg (3.05 mumol), had an apparent decrease in clearance at the higher doses. These findings are consistent with the fact that hydralazine is converted intravascularly to hydralazine pyruvic acid hydrazone and the fact that potentially saturable hepatic metabolic pathways play only a modest role in systemic clearance.

Dose-Response Relationship, Drug↗
PubMed1984

Effect of food on blood hydralazine levels and response in hypertension.

A study with a nonspecific hydralazine assay reported that food increased hydralazine concentrations in plasma. We used a specific HPLC hydralazine assay to determine the effect of food on hydralazine blood levels and hemodynamic responses after oral hydralazine. Six subjects with uncomplicated essential hypertension were given 1 mg/kg hydralazine solution orally on two occasions at least 3 days apart. On 1 study day subjects fasted and on the other they were given a standard meal 45 min before hydralazine. Mean arterial pressure and heart rate were monitored for 2 hr before and for 4 hr after hydralazine and frequent venous blood samples were drawn for hydralazine assay. Hepatic blood flow was estimated by determination of indocyanine green clearance before food, after food, and 30 min after hydralazine. Peak blood hydralazine concentrations fell in all (46.2% +/- 11.5%; means +/- SE) and areas under the blood hydralazine concentration/time curves fell (45.7% +/- 9.5%) after food. This could not be explained by changes in liver blood flow. Food-related reductions in blood levels of hydralazine were associated with reduced vasodepressor effects (41.5% +/- 5.6%). It is possible that food increases intravascular conversion of hydralazine to hydralazine pyruvic acid hydrazone. The reduction in vasodepressor response suggests that patients with hypertension should take hydralazine at a fixed time in relation to meals.

Administration, Oral↗