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PubMed2005

Reaction of 5-aminosalicylic acid with peroxyl radicals: protection and recovery by ascorbic acid and amino acids.

PURPOSE: The aims of the study are to analyze the interaction between 5-aminosalicylic acid (5-ASA) and peroxyl radicals and to evaluate the effect of some endogenous compounds such as ascorbic acid and amino acids on the oxidation of 5-ASA induced by 2,2'-azo-bis(2-amidinopropane) dihydrochloride. METHODS: The consumption and/or the recovery of 5-ASA (7.6 microM) exposed to a peroxyl radical source [2,2'-azo-bis(2-amidinopropane)] was followed by techniques such as spectrofluorescence, high-performance liquid chromatography, and differential pulse voltammetry. RESULTS: 5-Aminosalicylic acid was found to readily react with peroxyl radicals at micromolar concentrations and to protect c-Phycocyanin in a very similar fashion to that shown by Trolox. Exposure of 5-ASA to peroxyl radicals led to its oxidation into the corresponding quinone-imine. Disappearance of 5-ASA was prevented by tryptophan, cysteine, glutathione, and ascorbic acid. Furthermore, some of these compounds induced the partial (cysteine and glutathione) or total (ascorbic acid) recovery of 5-ASA when added after its almost total consumption. CONCLUSIONS: 5-Aminosalicylic acid is a very efficient peroxyl radical scavenger. The 5-ASA oxidation by peroxyl radicals was prevented by ascorbic acid, cysteine, and glutathione. In addition, 5-ASA can be regenerated by these endogenous compounds, which would be a valuable mechanism to preserve 5-ASA in tissues undergoing oxidative stress conditions.

Amidines↗
PubMed1991

Identification of bile acid-CoA: amino acid N-acyltransferase in rat kidney.

A novel location of the bile-acid-conjugating enzyme bile acid-CoA:amino acid N-acyltransferase (BAT) has been discovered in the cytosolic fraction of rat kidney. Both taurine and glycine were utilized as substrates. Formation of bile acid N-acyl amidates was verified by h.p.l.c. by comparison with authentic standards and by specific hydrolysis using cholylglycine hydrolase. Immunoblot analysis using a human liver anti-BAT polyclonal antibody indicated that rat kidney BAT has the same molecular mass as rat liver BAT. These findings suggest that the kidney has a role in bile acid metabolism and physiology.

Acyltransferases↗
PubMed1996

kan-1 (bile acid CoA:amino acid N-acyltransferase) messenger RNA as a novel predictive indicator for prognosis of hepatocellular carcinoma patients after partial hepatectomy.

We identified kan-1 complementary DNA (cDNA), the sequence of which is identical to bile acid CoA:amino acid N-acyltransferase (BAT), a liver enzyme that catalyzes the conjugation of bile acids with glycine or taurine. Kan-1(BAT) messenger RNA (mRNA) levels of the resected specimens obtained from 37 hepatocellular carcinoma (HCC) patients were studied in an attempt to evaluate prognostic significance in HCC patients after partial hepatectomy. Using Northern blot hybridization, kan-1(BAT) mRNA levels were quantified in tumorous and nontumorous tissues, and the ratio of the former to the latter was defined as the kan-1(BAT) ratio. Twelve patients had a kan-1(BAT) ratio < 0.5 (low kan-1[BAT] ratio), and 25 patients had a ratio >0.5 (high kan-1[BAT] ratio). The patients with a low kan-1(BAT) ratio demonstrated poorer survival than the patients with a high kan-1(BAT) ratio (P = .0013). The overall estimated hazard ratio for death in patients with a low kan-1(BAT) ratio was 68.05 according to a multivariate model (P = .0005). Thus, the kan-1(BAT) ratio may serve as a new molecular prognostic marker in HCC patients, following hepatic resection.

Acyltransferases↗
PubMed1987

Carbohydrate, organic Acid, and amino Acid composition of bacteroids and cytosol from soybean nodules.

Metabolites in Bradyrhizobium japonicum bacteroids and in Glycine max (L.) Merr. cytosol from root nodules were analyzed using an isolation technique which makes it possible to estimate and correct for changes in concentration which may occur during bacteroid isolation. Bacteroid and cytosol extracts were fractionated on ion-exchange columns and were analyzed for carbohydrate composition using gas-liquid chromatography and for organic acid and amino acid composition using high performance liquid chromatography. Analysis of organic acids in plant tissues as the phenacyl derivatives is reported for the first time and this approach revealed the presence of several unknown organic acids in nodules. The time required for separation of bacteroids and cytosol was varied, and significant change in concentration of individual compounds during the separation of the two fractions was estimated by calculating the regression of concentration on time. When a statistically significant slope was found, the true concentration was estimated by extrapolating the regression line to time zero. Of 78 concentration estimates made, there was a statistically significant (5% level) change in concentration during sample preparation for only five metabolites: glucose, sucrose, and succinate in the cytosol and d-pinitol and serine in bacteroids. On a mass basis, the major compounds in bacteroids were (descending order of concentration): myo-inositol, d-chiro-inositol, alpha,alpha-trehalose, sucrose, aspartate, glutamate, d-pinitol, arginine, malonate, and glucose. On a proportional basis (concentration in bacteroid as percent of concentration in bacteroid + cytosol fractions), the major compounds were: alpha-aminoadipate (94), trehalose (66), lysine (58), and arginine (46). The results indicate that metabolite concentrations in bacteroids can be reliably determined.

Journal Article↗
PubMed1980

Bimodal effects of cellular amino acids on Na+-dependent amino acid transport in Ehrlich cells.

Cells depleted of amino acids show lower rates of glycine or aminoisobutyric acid uptake than do freshly isolated cells. In the amino acid-depleted cells, addition of valinomycin stimulates amino acid influx at least to the level observed in freshly isolated cells. In cells containing high levels of cellular amino acids, valinomycin has little effect on influx of amino acids. It is concluded that the transport of amino acids in freshly isolated cells is elevated compared to depleted cells because the cells are hyperpolarized by the continuous loss of cellular amino acids during the transport assay. During this hyperpolarization by amino acid loss, transport of amino acids is not further stimulated by valinomycin at low external [K+] (10 mM +/- 5 mM). With the exception of preloading with glycine, cells preloaded with a single amino acid to a concentration greater than 20 mM show reduced rates of glycine and aminoisobutyric acid influx at early times (less than 15 min) compared to amino acid-depleted cells. The reduction of influx is transient and by 30 min, influx is greater in preloaded than in amino acid-depleted cells. Knowing that increases and decreases in the membrane potential are achieved by using varying external [K+] in the presence of valinomycin and propranolol, and using amino acid-depleted cells, it can be shown that an increased membrane potential increases the V for glycine and aminoisobutyric acid influx. A decrease in the potential difference results in a decreased V. Changes in Km also occur when the membrane potential is varied.

Amino Acids↗
PubMedDate not supplied

Incorporation of fatty acids and amino acids by cultured Pneumocystis carinii.

Cultured P. carinii rapidly took up a variety of fatty acids. The relative rates of uptake for four fatty acids were 18:1 >> 16:0 approximately equal to 18:0 approximately equal to 18:2. Fatty acids were primarily incorporated into phospholipids and the uptake process was specifically inhibited by 2.2 and 22 microM primaquine, a concentration having no effect on host cells. Amino acids were also taken up by cultured P. carinii in a primaquine sensitive process. Radiolabeled leucine was incorporated into the major surface glycoprotein of P. carinii. The formation of radioactive P. carinii-specific proteins indicated that the cultured organisms carried out transcription and translation and that the incorporation of amino acids was dependent upon P. carinii rather than rare HEL human embryonic lung cells. The spinner flask culture system provides convenient access to P. carinii for metabolic studies in defined medium for a period of 5-14 days after inoculation.

Animals↗
PubMed1998

Sodium-dependent homo- and hetero-exchange of neutral amino acids mediated by the amino acid transporter ATB degree.

We have investigated the functional characteristics of the human amino acid transporter ATB degree using the Xenopus laevis oocyte expression system. When expressed in oocytes, ATB degree mediates the uptake of neutral amino acids in an Na(+)-dependent manner. In addition, this transporter is able to mediate the efflux of intracellular neutral amino acids in exchange with extracellular neutral amino acids. This homo- and hetero-exchange of amino acids is absolutely Na(+)-dependent and conforms strictly to the substrate specificity of ATB degree. Kinetic analysis indicates that the affinity of ATB degree for a given amino acid substrate is similar whether ATB degree catalyzes the influx of the amino acid or the amino acid-induced efflux of intracellular amino acids. These results demonstrate for the first time the ability of ATB degree to function as a homo- and hetero-exchanger for its substrates.

Amino Acid Transport Systems↗
PubMed1997

Using the radial distributions of physical features to compare amino acid environments and align amino acid sequences.

We have performed a comprehensive analysis of the microenvironments surrounding the twenty amino acids. Our analysis includes comparison of amino acid environments with random control environments as well as with each of the other amino acid environments. We describe the amino acid environments with a set of 21 features summarizing atomic, chemical group, residue, and secondary structural features. The environments are divided into radial shells of 1 A thickness to represent the distance of the features from the amino acid C beta atoms. We make the results of our analysis available graphically over the world wide web. To illustrate the validity and utility of our analysis, we used the amino acid comparative profiles to construct a substitution matrix, the WAC matrix, based on a simple summary of the computed environmental differences. We compared our matrix to BLOSUM62 and PAM250 in BLAST searches with query sequences selected from 39 protein families found in the PROSITE database. Although BLOSUM62 was the most sensitive matrix overall, our matrix was more sensitive for some families, and exhibited overall performance similar to PAM250. Our results suggest that the radial distribution of biochemical and biophysical features is useful for comparing amino acid environments, and that similarity matrices based on the geometric distribution of features around amino acids may produce improved search sensitivity.

Amino Acid Sequence↗
PubMed1991

Thermodynamic parameters for the glutamate dehydrogenase catalyzed alpha-imino acid-alpha-amino acid interconversion.

Delta 1-Piperidine 2-carboxylic acid, an alpha-imino acid, is reduced by 1,4-dihydropyridines to pipecolic acid, an alpha-amino acid, and the corresponding pyridinium ions. This nonenzymatic reaction occurs only in the direction of pipecolic acid production. Glutamate dehydrogenase catalyzes this reaction when the reductant is NADPH and gives as products L-pipecolic acid and NADP+. The reaction velocity for the enzyme-catalyzed reaction is measurable in either direction. The pH-independent equilibrium constant, Keq, for the reduction of the imino acid by NADPH to give pipecolic acid anion and NADP+ was determined from the equilibrium conditions and the pKa values of pipecolic acid (10.72) and of the cyclic imino acid (8.10). The value of Keq was found to be 175 +/- 30; the values of delta G0, delta H0 and delta S0 are -3.1 +/- 0.1 kcal/mol, 5 +/- 1 kcal/mol and 27 +/- 4 e.u., respectively. The data indicate that the reactants are far more solvated than the products and that there must be a large degree of solvent reorganization during the course of the reaction. If these thermodynamic parameters apply to the redox step of the enzyme-catalyzed glutamate reaction, then the burst phase which results upon mixing the enzyme, L-glutamate and NADP+ in stoichiometric amounts must contain a hidden nonredox step of large delta H0 value to account for the curved Arrhenius plot observed for this phase (A.H. Colen, R.T. Medary and H.F. Fisher, Biopolymers 20 (1981) 879).

Amino Acids↗
PubMed2001

Characterization of a mouse colonic system B(0+) amino acid transporter related to amino acid absorption in colon.

Previous experiments have shown that an amino acid transport system B(0+) transporter in cultured colonic epithelial cells mediates amino acid absorption. Here we describe the cloning and functional characterization of a system B(0+) transporter selectively expressed in the colon. Using the combination of an expressed sequence tag database search and RT-PCR approaches, we cloned a mouse colonic amino acid transporter, designated mCATB(0+). Northern blot analysis revealed that mCATB(0+) was selectively expressed in the large intestine. In situ hybridization showed the mCATB(0+) mRNA to be localized in absorptive epithelial cells. When expressed in Xenopus oocytes, mCATB(0+) exhibited a Na(+)-dependent stereoselective uptake and a broad specificity for neutral and cationic amino acids, which is characteristic of amino acid transport system B(0+). In vivo [(3)H]glycine uptake assay demonstrated that a system B(0+)-like transporter protein was expressed on the apical surface of the colonic absorptive cells. Our data suggest that a mouse colonic amino acid transporter mCATB(0+) may absorb amino acids from the intestinal contents in the colon.

Amino Acid Sequence↗
PubMed1985

Release of endogenous dopamine, 3,4-dihydroxyphenylacetic acid, and amino acid transmitters from rat striatal slices.

The release of endogenous dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) was measured in superfused striatal slices of the rat and the results compared with data obtained for the release of endogenous (a) DA and DOPAC in the cerebral cortex, nucleus accumbens and thalamus; (b) 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), GABA, and glutamate in the striatum; and (c) GABA, glutamate and 5-HT in the cerebral cortex. In superfused slices of all four CNS regions, there appeared to be a Ca2+-dependent, K+-stimulated release of endogenous DA. In addition, in slices of the striatum and nucleus accumbens there also appeared to be a Ca2+ -dependent, 60 mM K+ stimulated release of endogenous DOPAC. In the striatum, 16 mM Mg2+ was as effective as 2.5 mM Ca2+ in promoting the 60 mM K+-stimulated release of DOPAC. In addition, 16 mM Mg2+ appeared to function as a weak Ca2+ agonist since it also promoted the release of DA to approximately 40% of the level attained with Ca2+ in the presence of 60 mM K+. On the other hand, in the striatum, 16 mM Mg2+ inhibited the Ca2+-dependent, 60 mM K+-stimulated release of GABA and glutamate. Similar Mg2+-inhibition was observed in the cerebral cortex not only for GABA and glutamate but also for DA and 5-HT. With the use of alpha-methyl rho-tyrosine (tyrosine hydroxylase inhibitor), cocaine (uptake inhibitor) and pargyline (monoamine oxidase inhibitor), it was determined that most of the released DA and DOPAC was synthesized in the slices during the superfusion; DOPAC was not formed from DA which had been released and taken up; and DA and DOPAC were released from DA nerve terminals. In addition, the data indicate a difference in the release process between the amino acids and the monoamines from striatal slices since Mg2+ inhibited the Ca2+-dependent, K+-stimulated release of GABA and glutamate and appeared to promote the release of DA and 5-HT.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2004

Portal drained visceral flux, hepatic metabolism, and mammary uptake of free and peptide-bound amino acids and milk amino acid output in dairy cows fed diets containing corn grain steam flaked at 360 or steam rolled at 490 g/L.

Objectives were to measure net fluxes of free (FAA) and peptide bound amino acids (AA) (PBAA) across portal-drained viscera (PDV), liver, splanchnic, and mammary tissues, and of milk AA output of lactating Holstein cows (n = 6, 109 +/- 9 d in milk) as influenced by flaking density of corn grain. Cows were fed alfalfa-based total mixed ration (TMR) containing 40% steam-flaked (SFC) or steam-rolled corn (SRC) grain. The TMR were offered at 12-h intervals in a crossover design. Six sets of blood samples were obtained from indwelling catheters in portal, hepatic, and mammary veins and mesenteric or costoabdominal arteries every 2 h from each cow and diet. Intake of dry matter (18.4 +/- 0.4 kg/d), N, and net energy for lactation were not altered by corn processing. Milk and milk crude protein yields (kg/12-h sampling) were 14.2 vs. 13.5 and 0.43 vs. 0.39 for cows fed SFC or SRC, respectively. The PDV flux of total essential FAA was greater (571.2 vs. 366.4 g/12 h, SEM 51.4) in cows fed SFC. The PDV flux of total essential PBAA was 69.3 +/- 10.8 and 51.5 +/- 13.2 g/12 h for cows fed SFC and SRC, respectively, and differed from zero, but fluxes of individual PBAA rarely differed between treatments. Liver flux of essential FAA was greater in cows fed SRC, but only the PBAA flux in cows fed SRC differed from zero. Splanchnic flux of FAA and PBAA followed the pattern of PDV flux, but variation was greater. Mammary uptake (g/12 h) of total essential FAA was greater in cows fed SFC than SRC (224.6 vs. 198.3, SEM 7.03). Mammary uptake of essential PBAA was 25.0 vs. 15.1, SEM 5.2, g/12 h for cows fed SFC or SRC, respectively, and differed from zero in half of the PBAA. Milk output of EAA was 187.8 vs 175.4, SEM 4.4 g/12 h in cows fed SFC and SRC, respectively, and output of most essential AA consistently tended to be greater in cows fed SFC. It is apparent that PBAA comprise a portion of total AA flux across PDV and are affected by grain processing. Further, this pool supplies an important component of AA taken up by the mammary gland. Quantifying the contribution of PBAA may improve diet formulation with respect to intestinal absorption and mammary uptake of AA.

Amino Acids↗
PubMed2002

Amino acid availability affects amino acid flux and protein metabolism in the porcine mammary gland.

A kinetic model was used to examine transmembrane flux kinetics of lysine, methionine and valine across the porcine mammary gland (MG) under dietary amino acid (AA) limiting, adequate and excess conditions. Lactating sows (3 per treatment) were offered three diets: lysine-deficient [LD, 4.9 lysine and 9.9 valine (g/kg diet)], adequate (Control, 9.7 and 10.2) and valine-excess (VE, 9.8 and 13.4). On d 18 of lactation, 2-(15)N-lysine, 5-methyl-(2)H(3)-methionine and 1-(13)C-valine were infused into a jugular vein for 20.5 h. Milk and arterial and mammary venous blood samples were collected at 2- and 1-h intervals, respectively. Compared with Control, milk yield and litter growth rate decreased (P < 0.05) in sows fed the LD diet. Model estimates of mammary protein synthesis (PS), breakdown (PB) and net PS decreased (P < 0.05) in sows fed the LD diet. Net uptake of lysine decreased (P < 0.05) in sows fed the LD diet as a result of decreases in inward and outward transport of lysine. Inward transport of methionine tended to be reduced (P < 0.10) in sows fed the LD diet, resulting in a decrease in net methionine uptake. In sows fed the VE diet, PB was reduced (P < 0.05) and PS unchanged compared with Control. Outward transport of valine and net lysine uptake were reduced (P < 0.05), but net valine uptake was unchanged in sows fed the VE diet compared with Control. In conclusion, the kinetic model provided estimates of PS that were similar to empirical measurements of milk protein output and mammary protein accretion. Transport of lysine and methionine by the porcine MG is closely linked to regulation of mammary PS. Lysine availability has little effect on the transmembrane flux of valine.

Amino Acids↗
PubMed1972

Changes in free amino acid production and intracellular amino acid pools of Bacillus licheniformis as a function of culture age and growth media.

Changes in the endogenous intracellular amino acid pool and total free amino acid production in Bacillus licheniformis grown in minimal media were investigated. The total intracellular pool increased during exponential growth and then decreased rapidly after the end of growth. Most of the amino acids were present at low concentrations, but glutamate and alanine comprised 60 to 90% of the total intracellular free amino acid at most times during the growth cycle. It was concluded that, in addition to providing monomers for protein synthesis, the intracellular amino acid pool may be maintained for the storage of energy-providing metabolic intermediates and possibly as a balance to the ionic strength of the medium. The total free amino acid production by the cell was found to be dependent upon the composition of the salts medium as well as the culture age under conditions in which the carbon and nitrogen sources were the same. A 10-fold increase in extracellular amino acid was observed as the cells changed from vegetative to sporulation metabolism, mostly due to the extrusion of intracellular amino acid. The impact of this increase upon amino acid uptake and pulse-labeling studies using unwashed cells is discussed.

Alanine↗
PubMed1985

Determination of 3-mercaptolactic acid by amino acid analyzer after aminoethylation.

A quantitative determination of 3-mercaptolactic acid was performed after its conversion into S-aminoethylmercaptolactic acid by reacting with excess of 2-bromoethylamine. S-aminoethylmercaptolactic acid was quantitated by an amino acid analyzer. Other thiols were shown not to interfere with the determination of 3-mercaptolactic acid. The sensitivity of the method was at the nanomoles level. The application of the method to the determination of 3-mercaptolactic acid in human urine is also reported.

Amino Acids, Sulfur↗
PubMed2003

Hamster D-amino-acid oxidase cDNA: rodents lack the 27th amino acid residue in D-amino-acid oxidase.

The nucleotide sequence of cDNA that encodes hamster d-amino-acid oxidase (DAO) was determined. The cDNA consisted of 1,590 nucleotides and a poly(A) tail. It had an open reading frame for a protein consisting of 346 amino acid residues. The number of the amino acid residues is the same as that of the rat DAO. However, the hamster DAO has one residue more than mouse DAO and one residue less than human, pig, rabbit, and guinea pig DAOs. Amino acid sequence of the hamster DAO was highly similar to those of mouse and rat DAOs: 89% and 88% of the amino acid residues were identical between the hamster and mouse DAOs and between the hamster and rat DAOs, respectively. The homology was slightly less between the hamster DAO and the human (81%), pig (78%), rabbit (78%), or guinea pig DAO (82%). It has been proposed that the mouse and rat DAOs lack an amino acid residue corresponding to the 25th residue of the DAOs of other mammals. However, a detailed comparison of the amino acid sequences as well as the underlying nucleotide sequences by inclusion of the hamster ones revealed that the rodent DAOs does not lack the 25th, but the 27th residue.

Amino Acid Sequence↗
PubMedDate not supplied

Inhibition of bile flow in the isolated perfused rat liver by a synthetic parenteral amino acid mixture: associated net amino acid fluxes.

To identify a role for amino acids in cholestasis associated with total parenteral nutrition, we measured bile formation by the isolated perfused rat liver in the presence and absence of added amino acids. All livers were infused constantly with sodium [14C]taurocholate (0.28 mumoles per min) for 90 min. At 40 min, a primed-constant infusion of a synthetic L-amino acid mixture (121 + 19.3 mumoles of N per min) was administered for an additional 50 min. Mean bile flow rates during the amino acid infusion were reduced from 15.4 microliter per min per 10 gm liver weight to 10.4 microliter per min per 10 gm (p less than 0.005). There was no significant change during saline infusion of control livers, and there was no significant difference in perfusate osmolalities in the two groups. Although biliary recovery of infused taurocholate was slightly lower in the experimental perfusions than in controls (95.3% vs. 101.7%, p less than 0.05), there was no significant reduction in taurocholate excretion rate during the infusion in either group. Bile flow changes were related to ambient concentrations and net fluxes of individual amino acids in the perfusate. Of the 14 infused amino acids, glycine and arginine achieved levels greater than 3 times greater than reported physiological postprandial portal venous concentrations in the rat, and together constituted about 25% of the 90-min perfusate amino acids (8.3 mM). The highest net hepatic uptake was for glycine (125 mumoles per hr per 10 gm), which was almost 50% of its infusion rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1990

The effects of changes in plasma amino acid concentrations on erythrocyte amino acid content.

In order to determine the effects of large variations in plasma amino acid concentrations upon human erythrocyte amino acid content, the plasma concentration of blood samples was enhanced (x 3.8) by adding amino acids or decreased (x 0.49) by plasma dilution. Before and after incubation (30 s at 37 degrees C), the erythrocyte contents were calculated from whole blood and plasma amino acid concentrations. Large and rapid plasma concentration variations led to significant erythrocyte changes in 11 amino acids. THR, CIT, alpha AB, VAL, MET, ILE, LEU, TYR, PHE, TRP, and ARG. Relationships between erythrocyte and plasma concentrations were determined for these amino acids. These observations were examined in the light of the role played by erythrocytes in blood amino acid transport.

Amino Acids↗