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PubMed1978

Production of valine by a Bacillus sp.

A bacterium isolated from Burdwan (India) soil was found to accumulate L-valine in the growth medium and identified to be a strain of Bacillus subtilis. The strain is able to grow and accumulate valine in a purely synthetic medium, but supplementation of the synthetic medium with either Casamino acids or yeast extract or with both, significantly improves the yield. The entire fermentation period can be divided into a growth phase and a production phase, which can be prolonged by adjustment of pH to the neutral range. Among the different carbon and nitrogen sources tested glucose at 8.5% and L-glutamic acid at 0.8%, respectively, were found most suitable. Cane sugar molasses tested as a substitute for glucose significantly stimulated growth but valine production was less. Different vitamins tested stimulated growth and valine yield and an inoculum level of 10% (v/v) of the medium was found to be optimal. The yield of valine under optimal conditions was found to be 4.53 g per litre of the medium. Valine has been isolated in crystalline form from the fermented broth by ion exchange resin chromatography and found to be a pure sample of the L-isomer.

Bacillus subtilis↗
PubMed1994

Coordinated expression of valine catabolic enzymes during adipogenesis: analysis of activity, mRNA, protein levels, and metabolic consequences.

3T3-L1 fibroblasts have limited enzymatic capacity to oxidize valine. Enzymes expressed in these cells allow efficient oxidation of only the first carbon of this branched chain amino acid. The pathway is effectively truncated at the level of 3-hydroxyisobutyrate because of very low expression of two enzymes required for the complete pathway, 3-hydroxyisobutyrate dehydrogenase and methylmalonate semialdehyde dehydrogenase. These two enzymes, as well as the branched chain alpha-ketoacid dehydrogenase, are markedly induced upon differentiation of 3T3-L1 fibroblasts into adipocytes. Flux through the first two decarboxylation steps of valine catabolism is increased dramatically after differentiation, particularly through the step catalyzed by methylmalonate semialdehyde dehydrogenase. Activation of the distal portion of the valine catabolic pathway correlates with significant increases in enzyme protein and mRNA levels for 3-hydroxyisobutyrate dehydrogenase and methylmalonate semialdehyde dehydrogenase, and this establishes the pathway in 3T3-L1 adipocytes for utilization of valine carbon for lipogenesis. The induction profiles of 3-hydroxyisobutyrate dehydrogenase and methylmalonate semialdehyde dehydrogenase are very similar, suggesting coordinate regulation of the expression of these two valine pathway-specific enzymes. Induction of valine catabolism in 3T3-L1 cells is solely differentiation dependent, suggesting regulation by the same factors that govern differentiation of 3T3-L1 fibroblasts into adipocytes.

1-Methyl-3-isobutylxanthine↗
PubMed1977

Growth inhibition of Escherichia coli K-12 by L-valine: a consequence of a regulatory pattern.

We studied the production of the ilvG gene product, the valine resistant acetolactate synthase isoenzyme II, in an ilvO+ G+ ilvB ilvHI derivative of Escherichia coli K-12. This strain contains mutations in the structural genes for the valine sensitive acetolactate synthase isoenzymes I and III. We find that the ilvG gene is not expressed in this strain when gworn with either isoleucine and valine or with isoleucine, leucine and valine, or when limited for either isoleucine or valine. Since we previously found that the ilvG gene is expressed in an ilvO603 containing strain (Favre et al., 1976), we presume that the mechanism by which E. coli K-12 regulates the ilv gene cluster is responsible for the lack of ilvG expression in the ilvO+ strain. The valine sensitivity of E. Coli K-12 is a consequence of this regulatory pattern.

Acetolactate Synthase↗
PubMed1987

Inhibition of fibroblast proliferation in a culture of human endometrial stromal cells using a medium containing D-valine.

A nutrient medium in which D-valine was substituted for L-valine inhibited fibroblast proliferation in a culture of human endometrial stromal cells. Fibroblasts were not killed by D-valine and were able to grow again when D-valine was replaced by L-valine. The stromal cells proliferate in the D-valine medium only when seeded at high density. They were distinguished from fibroblasts by their morphology in light microscopy, their surface characteristics at scanning electron microscopy and their lower staining with fibronectin antibodies.

Cell Division↗
PubMed1982

Mouse mammary cells in D-valine medium.

Cells of a mouse mammary epithelial cell line as well as fibroblasts from a mouse mammary explant were severely inhibited from proliferating in a medium in which D-valine was substituted for L-valine. After the first few days in D-valine medium, the number of epithelial cells did not increase despite the fact that a few percent continued to synthesize DNA. The cells did recognize the presence of the D-valine in the medium because cells in D-valine increased in volume and their numbers remained stationary, whereas cells without valine shrank and the cell numbers decreased with time.

Animals↗
PubMed1984

Characterization of valine transport in sea urchin eggs.

In unfertilized eggs, the mechanism of valine uptake can be summarized as follows. It is saturable over the external concentration of valine and insensitive to the presence of external sodium, depletion of cellular energy supplies and intracellular acidosis. The activation energy for the transport reaction (16.3 kcal/mol) is within the range of values reported for active transport of small molecules. In fertilized eggs, the total rate of valine uptake can be divided into two components: (i) a Na+-insensitive uptake which accounts for about 7% of total absorption as shown by studies in Na+-free medium seems to possess the same characteristics as in unfertilized eggs, (ii) a Na+-dependent transport of valine which constitutes the main entry is formed about 5 min after fertilization. It follows Michaelis-Menten kinetics characterized by 15-fold increase in Vmax with no change in Km. These two mechanisms have characteristics in common, such as their insensitivity to metabolic energy supply, their energy of activation and their ability to concentrate valine. The relationship between the establishment of the Na+-dependent valine uptake and the ionic events triggered by fertilization is discussed.

Amino Acids↗
PubMed1981

Normal valine disposal in obese subjects with impaired glucose disposal: evidence for selective insulin resistance.

Insulin has major effects on both glucose and branched chain amino acid metabolism. To determine whether the insulin resistance of obesity equally affects both glucose and branched chain amino acid metabolism, we measured the ability of obese and normal subjects to dispose of intravenous bolus dose of glucose (25 g) or L-valine (4 g). Basal plasma glucose levels were the same in the 18 normal and 17 obese (163 plus or minus 8% of ideal body weight) subjects, but basal plasma insulin levels were higher in the obese group (15 plus or minus 2 vs 6 plus or minus 1 microU/ml; p less than 0.001). The obese group had a slower glucose disappearance rate after glucose challenge (0.84 plus or minus 0.06 vs. 1.11 plus or minus 0.07 hr(-1); p less than 0.01) despite having a greater serum insulin response to the glucose load (26 plus or minus 4 vs 11 plus or minus 1 insulin area units; p less than 0.01), confirming insulin resistance. In contrast, disposal of a valine load was the same in normal and obese subjects, as assessed by initial and second phase exponential disappearance rates, metabolic clearance rates of valine, and volumes of distribution. In normal men, disposal rates of glucose and valine after simultaneous administration of both substances were slower than corresponding disposal rates determined when each substance was given alone. We conclude that obese subjects with impaired glucose disposal have normal valine disposal, suggesting that the insulin resistance of obesity can be selective in its effect on different metabolic systems. Glucose and valine also appear to mutually antagonize each other's disposal.

Blood Glucose↗
PubMed1995

Purification and characterization of a novel valine dehydrogenase from Streptomyces aureofaciens.

The first valine dehydrogenase of S. aureofaciens had been described (Vancurová, I., Vancura, A., Volc, J., Neuzil, J., Flieger, M., Basarová, G. and Bĕhal, V. (1988) J. Bacteriol. 170, 5192-5196). In the present work, a second valine dehydrogenase was detected and purified by hydrophobic and fast protein liquid chromatographies. The enzyme has a relative molecular mass (M(r)) of 240,000 and is composed of 6 identical subunits, each of M(r) 41,000. In the presence of NAD, the enzyme catalyzes the reversible deamination of several branched- and straight-chain amino acids. The enzyme activities with L-2-aminobutyrate and deamino-NAD+ are markedly higher than those with L-valine and NAD+, respectively. The enzyme synthesis is significantly induced by L-valine but severely repressed by ammonia. Molecular and catalytic properties of the enzyme distinguish it from the other described valine dehydrogenases. The results directly demonstrate the presence of two valine dehydrogenases in a single Streptomyces species.

Amino Acid Oxidoreductases↗
PubMed2004

Binding energies of water to lithiated valine: formation of solution-phase structure in vacuo.

Dissociation kinetics for loss of a water molecule from hydrated ions of lithiated valine, alanine ethyl ester and betaine are determined using blackbody infrared radiative dissociation at temperatures between -60 and 110 degrees C. From master equation modeling of these data, values of the threshold dissociation energy are obtained for clusters containing one through three water molecules. By comparing the values for valine with its two isomers, one a model for the nonzwitterion structure, the other a model for the zwitterion structure, information about the structure of valine in these hydrated clusters is inferred. Structures, relative energies, and water binding energies for these ions are also calculated at the B3LYP/6-31++G** level of theory. With one water molecule, both experiment and theory indicate that valine is not a zwitterion and that the lithium ion coordinates with the amino nitrogen and the carbonyl oxygen (NO coordinated) and the water molecule interacts directly with the lithium ion. With two water molecules, the zwitterion and nonzwitterion structures are nearly isoenergetic, but the experiment clearly indicates a NO-coordinated nonzwitterion structure. With three water molecules, both the experimental data and theory indicate that the lithium ion binds to the carboxylate group of valine, i.e., valine is zwitterionic with three water molecules. The agreement between the experimentally determined and calculated binding energies is good for all the clusters, with deviations of <== 0.12 eV.

Alanine↗
PubMed1999

The effects of paradoxical sleep deprivation and valine on spatial learning and brain 5-HT metabolism.

We have previously reported that rapid eye movement sleep deprivation (REMSD), induced by the flower pot technique, causes a deficit in reference spatial memory and increases rates of serotonin (5-HT) metabolism in the brain. In this study we used increased concentrations of dietary valine to inhibit tryptophan (TRP) transport across the blood-brain barrier in an attempt to modify the REMSD-induced increase of 5-HT metabolism. Rats were fed either a control diet or the same diet supplemented to 2% by weight valine, and were allocated to one of three experimental groups: cage control (CC), stress tank control (TC), or REMSD. Reference and working spatial memory of all rats was tested in a Morris water maze on Days 2, 3, and 4. REMSD produced a significant decrement in reference memory on Days 2 and 4, independent of dietary condition. The valine diet had a detrimental effect on the reference memory of TC rats on Day 2 but not Day 4. Measurements made on Day 4 indicated that the valine diet decreased brain TRP only in the CC rats. In contrast, the valine diet did not prevent increases in brain TRP or 5-HT metabolism in REMSD rats, and increased hypothalamic and brain stem TRP concentrations and the hippocampal 5-HIAA/5-HT ratio in TC rats. These results indicate that dietary valine does not prevent REMSD-induced changes in spatial memory or serotonin metabolism, although it does reduce brain TRP in nonstressed rats.

Animals↗
PubMed1978

Carbon and nitrogen nutrition of Aerobacter aerogenes for valine production.

A number of carbon and nitrogen compounds were tested for their effect on growth of Aerobacter aerogenes and valine production. Sucrose was found to be the superior carbon source for valine production, while mannose supported maximum cellular growth with very poor yield of valine. Urea was found to be the adequate nitrogen source for valine production. Supplementation of the synthetic medium with complex nutrients lowered the yield of valine. No direct relationship between the growth of the organism and the formation of the amino acid was noticed. On the basis of this study, a suitable synthetic medium for valine production has been developed.

Carbon↗
PubMed1998

Tolerance of a protein helix to multiple alanine and valine substitutions.

BACKGROUND: Protein stability is influenced by the intrinsic secondary structure propensities of the amino acids and by tertiary interactions, but which of these factors dominates is not known in most cases. We have used combinatorial mutagenesis to examine the effects of substituting a good helix-forming residue (alanine) and a poor helix-forming residue (valine) at many positions in an alpha helix of a native protein. This has allowed us to average over many molecular environments and assess to what extent the results reflect intrinsic helical propensities or are masked by tertiary effects. RESULTS: Alanine or valine residues were combinatorially substituted at 12 positions in alpha-helix lambda repressor. Functional proteins were selected and sequenced to determine the degree to which each residue type was tolerated. On average, valine substitutions were accommodated slightly less well than alanine substitutions. On a positional basis, however, valine was tolerated as well as alanine at the majority of sites. In fact, alanine was preferred over valine statistically significantly only at four sites. Studies of mutant protein and peptide stabilities suggest that tertiary interactions mask the intrinsic secondary structure propensity differences at most of the remaining residue positions in this alpha helix. CONCLUSIONS: At the majority of positions in alpha-helix lambda repressor, tertiary interactions with other parts of the protein can be viewed as an environmental "buffer" that help to diminish the helix destabilizing effects of valine mutations and allow these mutations to be tolerated at frequencies similar to alanine mutations.

Alanine↗
PubMed2000

Mutational analysis of invariant valine B12 in insulin: implications for receptor binding.

An invariant residue, valine B12, is part of the insulin B-chain central alpha-helix (B9-B19), and its aliphatic side chain lies at the surface of the hydrophobic core of the insulin monomer in close contact with the neighboring aromatic side chains of phenylalanines (B24 and B25) and tyrosines (B26 and B16). This surface contributes to the dimerization of insulin, maintains the active conformation of the insulin monomer, and has been suspected to be directly involved in receptor recognition. To investigate in detail the role of the B12 residue in insulin-receptor interactions, we have synthesized nine analogues bearing natural or unnatural amino acid replacements for valine B12 by chemical synthesis of modified insulin B-chains and the subsequent combination of each synthetic B-chain with natural insulin A-chain. The receptor binding potencies of the synthetic B12 analogues relative to porcine insulin were determined by use of isolated canine hepatocytes, and the following results were obtained: isoleucine, 13%; allo-isoleucine, 77%; tert-leucine, 107%; cyclopropylglycine, 43%; threonine, 5.4%; D-valine, 3.4%; alpha-amino-n-butyric acid, 14%; alanine, 1.0%; and glycine, 0.32%. Selected analogues were also analyzed by far-UV circular dichroic spectroscopy and by absorption spectroscopy of their complexes with Co(2+). Our results indicate that beta-branched aliphatic amino acids are generally tolerated at the B12 position with specific steric preferences and that the receptor binding potencies of these analogues correlate with their abilities to form dimers. Furthermore, the structure-activity relationships of valine B12 are quite similar to those of valine A3, suggesting that valine residues at both A3 and B12 contribute to the insulin-receptor interactions in a similar manner.

Amino Acid Substitution↗
PubMed1984

Metabolism of valine and 3-methyl-2-oxobutanoate by the isolated perfused rat kidney.

Metabolism of branched-chain amino and 2-oxo acids was studied in the isolated perfused kidney. Significant amounts of 2-oxo acids were released by perfused kidney with all concentrations of amino acids tested (0.1-1.0 mM each), despite the high activity of branched-chain 2-oxo acid dehydrogenase in kidney. As perfusate valine concentration was increased from 0.2 to 1.0 mM, [1-14C]valine transamination (2-oxo acid oxidized + released) increased roughly linearly; [1-14C]valine oxidation, however, increased exponentially. Increasing perfusate concentration of 3-methyl-2-oxo[1-14C]butanoate from 0 to 1.0 mM resulted in a linear increase in the rate of its oxidation and a rise in perfusate valine concentration; at the same time significant decreases occurred in perfusate isoleucine and leucine concentrations, with corresponding increases in rates of release of their respective 2-oxo acids. Comparison of rates of oxidation of [1-14C]valine and 3-methyl-2-oxo[1-14C]butanoate suggests that 2-oxo acid arising from [1-14C]valine transamination has freer access to the 2-oxo acid dehydrogenase than has the 2-oxo acid from the perfusate. The observations indicate that, when branched-chain amino and 2-oxo acids are present in perfusate at near-physiological concentrations, rates of transamination of the amino and 2-oxo acids by isolated perfused kidney are greater than rates of oxidation.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed2001

Evidence that the branched-chain amino acid L-valine prevents exercise-induced release of 5-HT in rat hippocampus.

The branched-chain amino acid L-valine competes with tryptophan for transport into the brain and has previously been shown to decrease brain 5-HT synthesis. The purpose of this study was to assess, using a combined venous catheterization and in vivo microdialysis method, the effect of pre-exercise L-valine administration on 5-hydroxytryptamine (5-HT) metabolism in the ventral hippocampus of rats submitted to an acute intensive treadmill running (120 min at 25 m x min(-1) followed by 150 min of recovery). The presented results include measurement of extracellular tryptophan (TRP), the 5-HT precursor, and extracellular 5-hydroxyindoleacetic acid (5-HIAA), the 5-HT metabolite. The data clearly demonstrate that exercise induces 5-HT release in the rat hippocampus: in control group, hippocampal 5-HT levels increase from 123.7 +/- 6.4% at the end of exercise to 133.9 +/- 6.4% after 60 min of recovery. Moreover, two hours of intensive running induced significant increases both in extracellular TRP levels (from 120 min of exercise to 30 min of recovery) and 5-HIAA levels (from 90 min of exercise to 90 min of recovery). Pre-exercise administration of L-valine prevents significantly the exercise-induced 5-HT release: 5-HT levels are maintained to baseline during exercise and recovery. With regard to the competitive effect of L-valine with TRP, we could observe a treatment-induced decrease in brain TRP levels (from 120 min of exercise to the end of recovery). Besides, L-valine does not prevent exercise-induced increase in 5-HIAA levels. The present study evidences that an acute intensive exercise stimulates 5-HT metabolism in the rat hippocampus, and that a pre-exercise administration of L-valine prevents, via a limiting effect on 5-HT synthesis, exercise-induced 5-HT release. This study provides some anwers to previous human and animal investigations, showing physiological and psychological benefits of branched-chain amino acids supplementation on performance.

Analysis of Variance↗
PubMed2003

Crystal structures of the CP1 domain from Thermus thermophilus isoleucyl-tRNA synthetase and its complex with L-valine.

Isoleucyl-tRNA synthetase (IleRS) links tRNA(Ile) with not only its cognate isoleucine but also the nearly cognate valine. The CP1 domain of IleRS deacylates, or edits, the mischarged Val-tRNA(Ile). We determined the crystal structures of the Thermus thermophilus IleRS CP1 domain alone, and in its complex with valine at 1.8- and 2.0-A resolutions, respectively. In the complex structure, the Asp(328) residue, which was shown to be critical for the editing reaction against Val-tRNA(Ile) by a previous mutational analysis, recognizes the valine NH(3)(+) group. The valine side chain binding pocket is only large enough to accommodate valine, and the placement of an isoleucine model in this location revealed that the additional methylene group of isoleucine would clash with His(319). The H319A mutant of Escherichia coli IleRS reportedly deacylates the cognate Ile-tRNA(Ile) in addition to Val-tRNA(Ile), indicating that the valine-binding mode found in this study represents that in the Val-tRNA(Ile) editing reaction. Analyses of the Val-tRNA(Ile) editing activities of T. thermophilus IleRS mutants revealed the importance of Thr(228), Thr(229), Thr(230), and Asp(328), which are coordinated with water molecules in the present structure. The structural model for the Val-adenosine moiety of Val-tRNA(Ile) bound in the IleRS editing site revealed some interesting differences in the substrate binding and recognizing mechanisms between IleRS and T. thermophilus leucyl-tRNA synthetase. For example, the carbonyl oxygens of the amino acids are located opposite to each other, relative to the adenosine ribose ring, and are differently recognized.

Amino Acid Sequence↗
PubMed1997

Transport of L-valine by the chicken caecum.

1. We have studied L-valine transport by the caecal segments of 6- to 8-week-old chickens. Isolated enterocytes from the proximal caecum incubated with 0.1 mM L-valine can accumulate the substrate against a concentration gradient. After 50 min incubation, the intracellular L-valine concentration reached 0.53 mM, a value higher than that observed in enterocytes from the jejunum (0.34 mM; P< 0.01). 2. Enterocytes from the medial and distal caccal regions are unable to transport L-valine uphill (cell concentration: 0.1 mM). 3. Amino acid accumulation by proximal caecal cells was Na+ -dependent and was inhibited by ouabain and 2,4-dinitrophenol. L-methionine inhibits L-valine uptake and a 2.5 mM concentration abolishes the capacity of enterocytes to accumulate the substrate. 4. The high accumulation ratios shown by the proximal caecum for L-valine suggest a role for this intestinal segment in the absorption of neutral amino acids present in the caecal chamber.

2,4-Dinitrophenol↗
PubMed1980

Leucine, isoleucine, valine and histidine requirements of fingerling channel catfish.

Growth studies were conducted with fingerling channel catfish to determine the minimal requirements for the amino acids leucine, isoleucine, valine and histidine. The experimental diets were formulated from purified ingredients to contain 24% crude protein and 275 kcal/100 g diet. Casein and gelatin served as protein sources and were supplemented with crystalline L-amino acids to provide the amino acid pattern found in 24% crude protein from whole egg powder. Based on dry diet the catfish required 0.84 +/- 0.04% leucine, 0.62 +/- 0.04% isoleucine, 0.71 +/- 0.03% valine and 0.37 +/- 0.01% histidine. These values correspond to 3.50% leucine, 2.58% isoleucine 2.96% valine and 1.54% histidine when expressed as a percentage of dietary protein. Quantitation of serum free amino acid levels revealed a marked increase in valine and isoleucine in leucine-deficient fish. In addition, increases in dietary isoleucine or valine resulted in changes in the serum levels of isoleucine, valine and leucine. These data indicate an apparent interaction among these amino acids in the catfish comparable to that previously observed in other species. Dietary histidine caused no increase in serum free histidine levels until the dietary requirement was reached. Muscle carnosine could not be detected in the catfish.

Amino Acids, Essential↗