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1.
Summary. In the kidney the proximal tubule is responsible for the uptake of amino acids. This occurs via a variety of functionally
and structurally different amino acid transporters located in the luminal and basolateral membrane. Some of these transporters
show an ion-dependence (e.g. Na+, Cl− and K+) or use an H+-gradient to drive transport. Only a few amino acid transporters have been cloned or functionally characterized in detail
so far and their structure is known, while little is known about a majority of amino acid transporters. Only few attempts
have been untertaken looking at the regulation of amino acid transport. We summarized more recent information on amino acid
transport in the renal proximal tubule emphasizing functional and regulatory aspects.
Received August 8, 1999; Accepted April 20, 2000 相似文献
2.
Summary. The effects of the amino acids D-ser, D-asp, and D-ala on lipoperoxidation under conditions of hypertension, alcoholism, and
ammonemia in rat liver and kidney mitochondria were studied. Under normal conditions, D-alanine increased in 54% free radicals
production in liver mitochondria (p < 0.05). The D-amino acids had no effect on kidney mitochondria. D-ser and D-ala increased lipoperoxidation in spontaneously
hypertensive rats (SHR) as compared with their normotensive genetic control Wistar-Kyoto (WKY) rats (p < 0.05). During hypertension and in oxidative stress in the presence of calcium, only D-ala produced 46% and 29% free radicals
in liver and kidney mitochondria (p < 0.05), respectively. During chronic alcoholism, D-ser increased lipoperoxidation in 80% in kidney mitochondria (p < 0.05), as compared to control. During ammonemia, D-ser produced 41% free radicals. 相似文献
3.
γ-Glutamyl compounds and their enzymatic production using bacterial γ-glutamyltranspeptidase 总被引:1,自引:0,他引:1
Summary. Some amino acids and peptides, which have low solubility in water, become much more soluble following γ-glutamylation. Compounds
become more stable in the blood stream with γ-glutamylation. Several γ-glutamyl compounds are known to have favorable physiological
effects on mammals. γ-Glutamylation can improve taste and can stabilize glutamine in aqueous solution. Because of such favorable
features, γ-glutamyl compounds are very attractive. However, only a small number of γ-glutamyl amino acids have been studied
although many other γ-glutamyl compounds may have characteristics that will benefit humans. This is mainly because γ-glutamyl
compounds have not been readily available. An efficient and simple method of producing various γ-glutamyl compounds, especially
γ-glutamyl amino acids, using bacterial γ-glutamyltranspeptidase has been developed. With this method, modifications of reactive
groups of the substrate and energy source such as ATP are not required, and a wide-range of γ-glutamyl compounds can be synthesized.
Moreover, bacterial γ-glutamyltranspeptidase, a catalyst for this method, is readily available from the strain over-producing
this enzyme. The superiority of producing γ-glutamyl compounds with bacterial γ-glutamyltranspeptidase over other methods
of production is discussed. 相似文献
4.
Summary. The cDNA encoding D-aspartate oxidase (DASPO) was cloned from mouse kidney RNA by RT–PCR. Sequence analysis showed that it
contained a 1023-bp open reading frame encoding a protein of 341 amino acid residues. The protein was expressed in Escherichia coli with or without an N-terminal His-tag and had functional DASPO activity that was highly specific for D-aspartate and N-methyl-D-aspartate. To investigate the roles of the Arg-216 and Arg-237 residues of the mouse DASPO (mDASPO), we generated
clones with several single amino acid substitutions of these residues in an N-terminally His-tagged mDASPO. These substitutions
significantly reduced the activity of the recombinant enzyme against acidic D-amino acids and did not confer any additional
specificity to other amino acids. These results suggest that the Arg-216 and Arg-237 residues of mDASPO are catalytically
important for full enzyme activity. 相似文献
5.
Bongcam V MacDonald-Comber Petétot J Mittendorf V Robertson EJ Leech RM Qin YM Hiltunen JK Poirier Y 《Planta》2000,211(1):150-157
The peroxisome targeting signal (PTS) required for import of the rat acyl-CoA oxidase (AOX; EC 1.3.3.6) and the Candida tropicalis multifunctional protein (MFP) in plant peroxisomes was assessed in transgenic Arabidopsis thaliana (L.) Heynh. The native rat AOX accumulated in peroxisomes in A. thaliana cotyledons and targeting was dependent on the presence of the C-terminal tripeptide S-K-L. In contrast, the native C. tropicalis MFP, containing the consensus PTS sequence A-K-I was not targeted to plant peroxisomes. Modification of the carboxy terminus
to the S-K-L tripeptide also failed to deliver the MFP to peroxisomes while addition of the last 34 amino acids of the Brassica napus isocitrate lyase, containing the terminal tripeptide S-R-M, enabled import of the fusion protein into peroxisomes. These
results underline the influence of the amino acids adjacent to the terminal tripeptide of the C. tropicalis MFP on peroxisomal targeting, even in the context of a protein having a consensus PTS sequence S-K-L.
Received: 19 July 1999 / Accepted: 19 February 2000 相似文献
6.
Hindi Sagit Grossman Dov P. Goldwaser Itzhak Shechter Yoram Fridkin Mati 《International journal of peptide research and therapeutics》2002,9(6):235-254
Summary L-glutamic acid (γ) monohydroxamate (L-Glu(γ)HXM) enhances the insulinomimetic activity of vanadium ions bothin vitro andin vivo. Based on this ligand as a lead compound, and in order to delineate molecular features relevant to its anti-diabetic potential,
14 related derivatives, including short peptides, were synthesized by solution as well as by solid phase methodologies. In
addition, hydroxamate derivatives of (+) pantothenic acid and D-biotin were prepared. The vanadium binding, capacity of the
hydroxamates synthesized was apparent, yet each had a different ligand-ions stoichiometry. Thein vitro lipogenic potency of several compounds toward rat adipocytes was demonstrated. Thus, vanadium complexes of L-Gln(α)HXM, L-Glu(γ)HXM-Gly,
L-Aad(δ)HXM, di-Glu-γ,γ-HXM and of (+) pantothenic acid hydroxamate exhibited 82, 79, 76, 39 and 39% of maximal insulin activity,
respectively. L-Aad (δ)HXM, L-Glu(γ)HXM-Gly and (+) pantothenic acid hydroxamate-by themselves —were found to possess 24,
14 and 10% of maximal insulin activity, respectively.In vivo potency, however, of L-Gln(α)HXM vanadium complex in streptozocin-treated rat diabetic model was less apparent. 相似文献
7.
Summary. The condensation reactions of sodium trimetaphosphate with single amino acids, namely glycine, L-alanine, β-alanine and γ-aminobutyric
acid or pairs of these amino acids were reinvestigated by electrospray ion-trap mass spectrometry and high performance liquid
chromatography. It was found when mixtures were treated by sodium trimetaphosphate only in the presence of α-amino acid dipeptides
were formed. Without addition of α-amino acids, the β-amino acid or γ-aminobutyric acid could not form peptide either by themselves
or with their mixtures under the same conditions. From the data it is concluded that phosphate might select α-amino acids
to produce the peptides being important precursors for the origin of life.
Authors’ address: Dr. Pengxiang Xu, The Key Laboratory for Chemical Biology of Fujian Province, Department of Chemistry, Xiamen
University, Xiamen 361005, China 相似文献
8.
Mesnard F Azaroual N Marty D Fliniaux MA Robins RJ Vermeersch G Monti JP 《Planta》2000,210(3):446-453
Nitrogen metabolism was monitored in suspension cultured cells of Nicotiana plumbaginifolia Viv. using nuclear magnetic resonance (NMR) spectroscopy following the feeding of (15NH4)2SO4 and K15NO3. By using two-dimensional 15N-1H NMR with heteronuclear single-quantum-coherence spectroscopy and heteronuclear multiple-bond-coherence spectroscopy sequences,
an enhanced resolution of the incorporation of 15N label into a range of compounds could be detected. Thus, in addition to the amino acids normally observed in one-dimensional
15N NMR (glutamine, aspartate, alanine), several other amino acids could be resolved, notably serine, glycine and proline. Furthermore,
it was found that the peak normally assigned to the non-protein amino-acid γ-aminobutyric acid in the one-dimensional 15N NMR spectrum was resolved into a several components. A peak of N-acetylated compounds was resolved, probably composed of the intermediates in arginine biosynthesis, N-acetylglutamate and N-acetylornithine and, possibly, the intermediate of putrescine degradation into γ-aminobutyric acid, N-acetylputrescine. The occurrence of 15N-label in agmatine and the low detection of labelled putrescine indicate that crucial intermediates of the pathway from glutamate
to polyamines and/or the tobacco alkaloids could be monitored. For the first time, labelling of the peptide glutathione and
of the nucleotide uridine could be seen.
Received: 29 March 1999 / Accepted: 15 July 1999 相似文献
9.
Summary. The influence of nitric oxide synthase (NOS) activity on the KCl-evoked amino acid concentrations was investigated by in vivo microdialysis in the striatum in a rat model of excitotoxic lesion. Basal microdialysate levels of amino acids decreased
during the quinolinic acid-induced neurodegeneration process, except for glutamine that increased initially and returned to
control values 30 days after quinolinic acid exposure. KCl-evoked increase of extracellular amino acid concentration was reduced
due to NOS activity in the striatum of both controls and lesioned animals, except for 120 days after quinolinic acid injection.
These changes of amino acid concentrations in microdialysates correlated with the known biochemistry of the consecutive domineered
cell types during the lesion process as revealed by histochemistry for NOS, NADPH-diaphorase, GFAP and isolectin B4. The present
data provide direct evidence that NOS activity can modulate extracellular amino acid concentrations in the striatum not only
under physiological conditions, but also during a pharmacologically induced lesion process and, thus, suggests that nitric
oxide affects neurodegeneration via this pathway.
Received October 20, 1999; Accepted February 25, 2000 相似文献
10.
Summary. A randomised, double blind, placebo-controlled study was performed giving 0.5 g · kg−1 · day−1 of undiluted alanyl-glutamine (20%) or saline in a peripheral vein during 4 hours in ICU patients (n = 20). During the infusion
period a steady state in plasma concentration was reached for alanyl-glutamine, but not for alanine, glutamine or glutamate.
On the other hand there was no accumulation of any of the amino acids, as the pre-infusion concentrations were reached within
8 hours after the end of infusion. The half-life of the dipeptide was 0.26 hours (range, 0.15–0.63 h). The distribution volume
of alanyl-glutamine was larger than the extracellular water volume, indicating a rapid hydrolysis of the dipeptide. There
was no detectable alanyl-glutamine in the urine of any of the patients. All patients had excretion of small amounts of amino
acids in urine, but the renal clearance of alanine, glutamine and glutamate were not different between the two groups. 相似文献
11.
Hultsch C Bergmann R Pawelke B Pietzsch J Wuest F Johannsen B Henle T 《Amino acids》2005,29(4):405-413
Summary. Isopeptide bonds between the ɛ-amino group of lysine and the γ-carboxamide group of glutamine are formed during strong heating
of pure proteins or, more important, by enzymatic reaction mediated by transglutaminases. Despite the wide use of a microbial
transglutaminase in food biotechnology, up to now little is known about the metabolic fate of the isopeptide Nɛ-(γ-glutamyl)-L-lysine. In the present study, N-succinimidyl-4-[18F]fluorobenzoate was used to modify Nɛ-(γ-glutamyl)-L-lysine at each of its two α-amino groups, resulting in the 4-[18F]fluorobenzoylated derivatives, for which biodistribution, catabolism, and elimination were investigated in male Wistar rats.
A significant different biochemical behavior of the two labelled isopeptides was observed in terms of in vitro stability, in vivo metabolism as well as biodistribution. The results suggest that the metabolic fate of isopeptides is likely to be dependent
on how they are reabsorbed – free or peptide bound. 相似文献
12.
Summary. The premise that free amino acid or dipeptide based diets will resolve the nutritional inadequacy of formulated feeds for
larval and juvenile fish and improve utilization of nitrogen in comparison to protein-based diets was tested in stomachless
fish, common carp (Cyprinus carpio L.) larvae. We examined the postprandial whole body free amino acid (FAA) pool in fish that were offered a FAA mixture based
diet for the duration of 2 or 4 weeks. We found that the total amount and all indispensable amino acids concentrations in
the whole body decreased after a meal. We then fed juvenile carp with dietary amino acids provided in the FAA, dipeptide (PP),
or protein (live feed organisms; brine shrimp Artemia salina nauplii, AS) forms. Histidine concentrations in the whole fish body increased in all dietary groups after feeding whereas
all other indispensable amino acids decreased in FAA and PP groups in comparison to the AS group. Taurine appears to be the
major osmotic pressure balancing free amino acid in larval freshwater fish which may indicate a conditional requirement. We
present the first evidence in larval fish that in response to synthetic FAA and PP diets, the whole body indispensable free
AA concentrations decreased after feeding. This study shows that amino acids given entirely as FAA or PP cannot sustain stomachless
larval fish growth, and may result in depletion of body indispensable AA and most of dispensable AA. The understanding of
these responses will determine necessary changes in diet formulations that prevent accelerated excretion of amino acids without
protein synthesis. 相似文献
13.
Summary. The main objective of the present study was to evaluate the in vivo and in vitro effect of Arg on serum nucleotide hydrolysis. The action of Nω-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase, on the effects produced by Arg was also examined.
Sixty-day-old rats were treated with a single or a triple (with an interval of 1 h between each injection) intraperitoneal
injection of saline (group I), Arg (0.8 g/kg) (group II), L-NAME (2.0 mg/kg or 20 mg/kg) (group III) or Arg (0.8 g/kg) plus
L-NAME (2.0 mg/kg or 20 mg/kg) (group IV) and were killed 1 h later. The present results show that a triple Arg administration
decreased ATP, ADP and AMP hydrolysis. Simultaneous injection of L-NAME (20 mg/kg) prevented such effects. Arg in vitro did not alter nucleotide hydrolysis. It is suggested that in vivo Arg administration reduces nucleotide hydrolysis in rat serum, probably through nitric oxide or/and peroxynitrite formation.
Both are first authors. 相似文献
14.
Cloning and expression of UDP-glucose: flavonoid 7-O-glucosyltransferase from hairy root cultures of Scutellaria baicalensis 总被引:1,自引:0,他引:1
A cDNA encoding UDP-glucose: baicalein 7-O-glucosyltransferase (UBGT) was isolated from a cDNA library from hairy root cultures of Scutellaria baicalensis Georgi probed with a partial-length cDNA clone of a UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT) from grape (Vitis vinifera L.). The heterologous probe contained a glucosyltransferase consensus amino acid sequence which was also present in the Scutellaria cDNA clones. The complete nucleotide sequence of the 1688-bp cDNA insert was determined and the deduced amino acid sequences
are presented. The nucleotide sequence analysis of UBGT revealed an open reading frame encoding a polypeptide of 476 amino
acids with a calculated molecular mass of 53 094 Da. The reaction product for baicalein and UDP-glucose catalyzed by recombinant
UBGT in Escherichia coli was identified as authentic baicalein 7-O-glucoside using high-performance liquid chromatography and proton nuclear magnetic resonance spectroscopy. The enzyme activities
of recombinant UBGT expressed in E. coli were also detected towards flavonoids such as baicalein, wogonin, apigenin, scutellarein, 7,4′-dihydroxyflavone and kaempferol,
and phenolic compounds. The accumulation of UBGT mRNA in hairy roots was in response to wounding or salicylic acid treatments.
Received: 8 September 1999 / Accepted: 4 October 1999 相似文献
15.
Cloning and heterologous expression of a rape cDNA encoding UDP-glucose:sinapate glucosyltransferase
A cDNA encoding a UDP-glucose:sinapate glucosyltransferase (SGT) that catalyzes the formation of 1-O-sinapoylglucose, was isolated from cDNA libraries constructed from immature seeds and young seedlings of rape (Brassica napus L.). The open reading frame encoded a protein of 497 amino acids with a calculated molecular mass of 55,970 Da and an isoelectric
point of 6.36. The enzyme, functionally expressed in Escherichia coli, exhibited broad substrate specificity, glucosylating sinapate, cinnamate, ferulate, 4-coumarate and caffeate. Indole-3-acetate,
4-hydroxybenzoate and salicylate were not conjugated. The amino acid sequence of the SGT exhibited a distinct sequence identity
to putative indole-3-acetate glucosyltransferases from Arabidopsis thaliana and a limonoid glucosyltransferase from Citrus unshiu, indicating that SGT belongs to a distinct subgroup of glucosyltransferases that catalyze the formation of 1-O-acylglucosides (β-acetal esters).
Received: 14 July 2000 / Accepted: 8 August 2000 相似文献
16.
Garcia RF Gazola VA Barrena HC Hartmann EM Berti J Toyama MH Boschero AC Carneiro EM Manso FC Bazotte RB 《Amino acids》2007,33(1):151-155
Summary. Our purpose was to determine the blood amino acid concentration during insulin induced hypoglycemia (IIH) and examine if the
administration of alanine or glutamine could help glycemia recovery in fasted rats. IIH was obtained by an intraperitoneal
injection of regular insulin (1.0 U/kg). The blood levels of the majority of amino acids, including alanine and glutamine
were decreased (P < 0.05) during IIH and this change correlates well with the duration than the intensity of hypoglycemia. On the other hand,
the oral and intraperitoneal administration of alanine (100 mg/kg) or glutamine (100 mg/kg) accelerates glucose recovery.
This effect was partly at least consequence of the increased capacity of the livers from IIH group to produce glucose from
alanine and glutamine. It was concluded that the blood amino acids availability during IIH, particularly alanine and glutamine,
play a pivotal role in recovery from hypoglycemia. 相似文献
17.
Phloem transport of amino acids in two Brassica napus L. genotypes and one B. carinata genotype in relation to their seed protein content 总被引:2,自引:0,他引:2
In order to investigate the relationship between the amino acid concentration in the phloem sap of leaves and the protein
content in seeds, two Brassica napus genotypes and one B. carinata genotype with low, medium and high seed protein contents were analyzed. Phloem sap was collected from the B. napus winter rapeseed breeding line DSV15 with 19% protein of dry weight in the seeds, the spring cultivar ‘Duplo’ with 25% protein
in the seeds and from the B. carinata line BRA1151/90 with 39% protein in the seeds by using the aphid-stylet technique. The total amino acid contents measured
in the phloem varied considerably among the three genotypes analysed, and correlated positively with their respective seed
protein contents. The total amino acid-to-sucrose ratio was lowest in B. napus line DSV15 which had the lowest seed protein content and highest in the B. carinata line BRA1151/90 which had the highest seed protein content. The amino-N translocation in the phloem during the light period
was about 2-fold higher in the B. carinata line BRA1151/90 than in the B. napus lines Dulpo and DSV15. Predominant amino acids in the phloem were glutamine and glutamate, followed by serine, aspartate,
and threonine. The amino acid patterns in the leaves resembled those in the phloem, although their absolute concentrations
were higher in the phloem than in the cytosol of mesophyll tissue. Furthermore, the concentration gradient of amino acids
between the cytosol of mesophyll cells and the phloem was higher in the B. carinata line BRA1151/90 than in the B. napus lines Duplo and DSV15. These results lead to the conclusion that the phloem translocation of amino-N and the phloem loading
process of amino acids are decisive factors for the protein content in the seeds of Brassica species.
Received: 28 November 1999 / Accepted: 10 April 2000 相似文献
18.
Summary. The influence of the operation conditions (temperature and residence time) of a thermic treatment on the total amount (free
and protein-bound) of amino acid enantiomers of dry fullfat soya was investigated. Total amino acid content was determined
using conventional ion-exchange amino acid analysis of total hydrolysates and chiral amino acid analysis was performed by
HPLC after precolumn derivatization with o-phthaldialdehyde and 1-thio-β-D-glucose tetraacetate. Contrary to corn that was investigated previously, notable racemization
was detected even at lower temperatures. At 140 °C the ratio of the D-enantiomer was 0.87% for glutamic acid, 2.81% for serine,
and 1.92% for phenylalanine; at 220 °C the ratios of the D-enantiomer of the above amino acids were 1.43, 4.61, and 4.68%,
respectively. The concentration of several L-amino acids decreased. At 220 °C there was 10% less L-glutamic acid, 17% less
L-serine, 5% less L-phenylalanine, 6.6% less L-aspartic, acid and 21% less L-lysine than in the control; their loss can be
assigned to different degrees of L – D conversion. While nearly complete transformation of L-phenylalanine can be attributed
to racemization, the main cause of the loss of L-lysine is not racemization. The treatments in the same order of magnitude
resulted in the formation of more D-amino acids and greater extent of racemization of amino acids in fullfat soya than that
of maize.
Authors’ address: J. Csapó, Faculty of Animal Science, Institute of Chemistry, University of Kaposvár, Guba S. u. 40., H-7400
Kaposvár, Hungary 相似文献
19.
Graham Noctor Ana-Carolina M. Arisi Lise Jouanin Marie-Hélène Valadier Yvette Roux Christine H. Foyer 《Planta》1997,202(3):357-369
Glutathione (GSH), γ-glutamylcysteine (γ-EC) and major free amino acids were measured in darkened and illuminated leaves
from untransformed poplars (Populus tremula × P. alba) and poplars expressing Escherichia coli genes for γ-glutamylcysteine synthetase (γ-ECS; EC 3.2.3.3) and glutathione reductase (GR; EC 1.6.4.2). In poplars overexpressing
γ-ECS, foliar γ-EC contents and GSH contents were markedly enhanced compared to poplars lacking the bacterial gene for the
enzyme. However, the quantitative relationship between the foliar pools of γ-EC and GSH in these transformants was markedly
dependent on light. In the dark, GSH content was relatively low and γ-EC content high, the latter being higher than the foliar
GSH contents of untransformed poplars in all conditions. Hence, this transformation appears to elevate γ-EC from the ranks
of a trace metabolite to one of major quantitative importance. On illumination, however, γ-EC content decreased fourfold whereas
GSH content doubled. Glutathione was also higher in the light in untransformed poplars and in those overexpressing GR. In
these plants, γ-EC was negligible in the light but increased in the dark. Cysteine content was little affected by light in
any of the poplar types. No light-dependent changes in the extractable activities of γ-ECS, glutathione synthetase (EC 3.2.3.2)
or GR were observed. In contrast, both the activation state and the maximum extractable activity of nitrate reductase (EC
1.6.6.1) were increased by illumination. In all poplar types, glutamate and aspartate were the major amino acids. The most
marked light-induced increases in individual amino acids were observed in the glutamine, asparagine, serine and glycine pools.
Illumination of leaves from poplars overexpressing γ-ECS at elevated CO2 or low O2 largely abolished the inverse light-dependent changes in γ-EC and GSH. Low O2 did not affect foliar contents of cysteine or glutamate but prevented the light-induced increase in the glycine pool. It
is concluded that light-dependent glycine formation through the photorespiratory pathway is required to support maximal rates
of GSH synthesis, particularly under conditions where the capacity for γ-EC synthesis is augmented.
Received: 17 December 1996 / Accepted: 28 January 1997 相似文献
20.
Summary. Amino acids analysis in single wheat embryonic protoplast was performed using capillary electrophoresis equipped with laser-induced
fluorescence (CE-LIF), combination with tissue culture technique. Reagent fluorescein isothiocyanate (FITC) was introduced
into living protoplasts by electroporation for intracellular derivatization. A special osmotic buffer (0.6 mol/L mannitol,
5 mmol/L CaCl2) was used to keep the osmotic balance of embryonic protoplasts during the protoplasts derivatization. After completion of
the derivatization reaction in the protoplasts, a single protoplast was drawn into the capillary tip by electroosmotic flow.
Then a 0.1 M NaOH lysing solution was injected by diffusion. The derivatized amino acids were separated by capillary electrophoresis
and detected by laser-induced fluorescence detection after the protoplast was lysed Nine amino acids were quantitatively and
qualitatively determined and compared in lysate and single protoplast of wheat embryonic cells respectively, with mean concentrations
of amino acids ranging from 2.68×10−5 mol/L to 18.18×10−5 mol/L in single protoplast. 相似文献