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PubMed2002

L-delta-(alpha-Aminoadipoyl)-L-cysteine-D-valine synthetase: production of dipeptides containing valine residue at its C-terminus.

L-delta-(alpha-Aminoadipoyl)-L-cysteine-D-valine synthetase (ACVS) has been recently studied as a model enzyme for peptide synthetases. It was found that in the absence of alpha-aminoadipic acid but in the presence of several cysteine analogues it was incorporated into several analogue dipeptides upon incubation of the potential cysteine analogues with ACVS. [(14)C]Cysteine was incorporated into the[(14)C]cysteinyl-valine analogue dipeptides. Notably, [(14)C]valine incorporation in the presence of N-acylated cysteine analogues was observed. The alpha-aminoadipic acid activation site is influential, inhibitory or promotive, on the production of these putative dipeptide products. The production of dipeptide analogues, containing valine or analogues at the C-terminus, leads to the speculation that the biosynthetic direction of ACV could be from the C-terminus to the N-terminus.

2-Aminoadipic Acid↗

PubMed2003

Characterisation of the enzyme activities involved in the valine biosynthetic pathway in a valine-producing strain of Corynebacterium glutamicum.

The enzyme activities of the valine biosynthetic pathway and their regulation have been studied in the valine-producing strain, Corynebacterium glutamicum 13032DeltailvApJC1ilvBNCD. In this micro-organism, this pathway might involve up to five enzyme activities: acetohydroxy acid synthase (AHAS), acetohydroxy acid isomeroreductase (AHAIR), dihydroxyacid dehydratase and transaminases B and C. For each enzyme, kinetic parameters (optimal temperature, optimal pH and affinity for substrates) were determined. The first enzyme of the pathway, AHAS, was shown to exhibit a weak affinity for pyruvate (K(m)=8.3 mM). It appeared that valine and leucine inhibited the three first steps of the pathway (AHAS, AHAIR and DHAD). Moreover, the AHAS activity was inhibited by isoleucine. Considering the kinetic data collected during this work, AHAS would be a key enzyme for further strain improvement intending to increase the valine production by C. glutamicum.

Acetolactate Synthase↗

PubMed1973

Isoleucine and valine metabolism in Escherichia coli. XXI. Mutations affecting derepression and valine resistance.

The activity of acetohydroxy acid isomeroreductase, an essential enzyme for isoleucine and valine biosynthesis in Escherichia coli, was examined in a series of mutants containing derepressed levels of acetohydroxy acid synthetase activity but which differed from each other in the sensitivity of the synthetases to valine inhibition. The finding that isomeroreductase was highest in the strain with the synthetase that was least sensitive to valine inhibition supported the model of internal induction of the isomeroreductase by its acetohydroxy acid substrates. The mutation leading to the acetohydroxy acid synthetase least sensitive to valine was found to be unlinked to the ilv gene cluster and appeared to result in a synthetase that differed from the normal enzyme in several properties. The locus of this mutation is designated ilvF. The loci leading to derepression were designated azl. A pleiotropic, apparently single-step, mutation was found that led to restoration of end-product sensitivity to the synthetase, loss of end-product sensitivity of threonine deaminase [EC 4.2.1.16, l-threonine hydro-lyase (deaminating) and loss of isomeroreductase activity.

Centrifugation, Density Gradient↗

PubMed1995

Influence of valine flooding on channeling of valine into tissue pools and on protein synthesis.

Rates of valine incorporation into protein were measured under control and valine-"flooding" conditions and included correction for the degree of recycling of unlabeled valine derived from the steady-state breakdown of tissue protein into the precursor pool (tRNA bound). The correction factor lambda, which is the ratio of the steady-state specific activity of valine in the tissue tRNA-bound pool to that in the arterial plasma, was determined for each of the tissues. In controls, values of lambda ranged from 0.31 in adrenals to 0.54 in heart; in flooded animals, values were higher, but only in liver was the value of lambda close to 1.0. In control and flooded rats, rates of protein synthesis were highest in liver and adrenals and lowest in skeletal muscle, with intermediate values in brain and heart. Flooding resulted in increased rates of protein synthesis in liver and decreased rates in adrenals. Rates of protein synthesis in brain, heart, and skeletal muscle were not statistically significantly affected by flooding.

Animals↗

PubMed1999

Steric interactions of valines 1, 5, and 7 in [valine 5, D-alanine 8] gramicidin A channels.

When the central valine residues 6, 7, and 8 of gramicidin A (gA) are shifted by one position, the resulting [Val(5), D-Ala(8)]gA forms right-handed channels with a single-channel conductance and average duration somewhat less than gA channels. The reduction in channel duration has been attributed to steric conflict between the side chains of Val(1) and Val(5) in opposing monomers (Koeppe, R. E. II, D. V. Greathouse, A. Jude, G. Saberwal, L. L. Providence, and O. S. Andersen. 1994. J. Biol. Chem. 269:12567-12576). To investigate the orientations and motions of valines in [Val(5), D-Ala(8)]gA, we have incorporated (2)H labels at Val 1, 5, or 7 and recorded (2)H-NMR spectra of oriented and nonoriented samples in hydrated dimyristoylphosphatidylcholine. Spectra of nonoriented samples at 4 degrees C reveal powder patterns that indicate rapid side chain "hopping" for Val(5), and an intermediate rate of hopping for Val(1) and Val(7) that is somewhat slower than in gA. Oriented samples of deuterated Val(1) and Val(7) show large changes in the methyl and C(beta)-(2)H quadrupolar splittings (Deltanu(q)) when Ala(5) in native gA is changed to Val(5). Three or more peaks for the Val(1) methyls with Deltanu(q) values that vary with the echo delay, together with an intermediate spectrum for nonoriented samples at 4 degrees C, suggest unusual side chain dynamics for Val(1) in [Val(5), D-Ala(8)]gA. These results are consistent with a steric conflict that has been introduced between the two opposing monomers. In contrast, the acylation of gA has little influence on the side chain dynamics of Val(1), regardless of the identity of residue 5.

Acylation↗

PubMed1992

Valine deficiency. 1. The effect of feeding a valine-deficient diet during the starter period on performance and feather structure of male broiler chicks.

Experiments were designed to investigate the effect of feeding diets deficient in one or more of the three branched-chain amino acids (BCAA) on the performance of 3-wk-old male broilers. In the first experiment, levels of .96 and 1.46% Leu, .52 and .82% Ile, and .65 and .95% Val were used. Feeding the lowest combination of the three BCAA resulted in weight gain (WG) and feed conversion ratio (FC) of 344 g and 1.59 g:g, respectively. These parameters were not improved by adding dietary increments of the three BCAA individually. The greatest response, however, for both WG (435 g) and FC (1.41 g:g) was obtained by the addition of the three BCAA simultaneously. Chicks fed the low-Val diets in combinations with added levels of Ile and Leu exhibited feather and leg abnormalities. A second experiment was designed to investigate the effect of Val deficiency on feather protein, feather amino acids, and calcium content of the bone. Three treatments were used: a BCAA-deficient diet with .96% Leu, .52% Ile, and .63% Val; a Val-deficient diet, which contained 1.37, .82, and .63% of Leu, Ile, and Val, respectively; and a Val-supplemented diet, which was the same as the previous diets except that the Val content was .83%. Valine deficiency significantly decreased WG (243 g), FC (1.69 g:g), bone calcium (134 mg/g dry bone), and feather protein (82.7% of wet weight). Valine deficiency also decreased the level of Cys in feathers, but increased those of Asp, Glu, Met, Tyr, His, and Lys.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids, Branched-Chain↗

PubMed1977

Solid phase synthesis and some hormonal activities of 1-deamino-4-L-valine-8-D-homolysine-and 1-deamino-4-L-valine-8-D-homoarginine-vasopressin.

1-Deamino-4-L-valine-8-DL-homolysine-vasopressin and protected 1-deamino-4-l-valine-8-D-lysine-vasopressin were synthesized by the solid phase method and were then converted into the title compounds (dVDHLVP and dVDHAVP) by tryptic digestion and epsilon-guanidination, respectively. The new hormone analogues exhibit only moderate antidiuretic potency, dVDHLVP 21 units/mg and dVDHAVP 31 units/mg, but since they are essentially devoid of pressor activity (o.o1 units/mg/ the A/P ratios are very high. In fact, dVDHLVP is the most specific antidiuretic agent in the lysine series known so far.

Amino Acid Sequence↗

PubMed2002

A study of conformational stability of poly(L-alanine), poly(L-valine), and poly(L-alanine)/poly(L-valine) blends in the solid state by (13)C cross-polarization/magic angle spinning NMR.

13C cross-polarization/magic angle spinning (CP/MAS) NMR and (1)H T(1rho) experiments of poly(L-alanine) (PLA), poly(L-valine) (PLV), and PLA/PLV blends have been carried out in order to elucidate the conformational stability of the polypeptides in the solid state. These were prepared by adding a trifluoroacetic acid (TFA) solution of the polymer with a 2.0 wt/wt % of sulfuric acid (H(2)SO(4)) to alkaline water. From these experimental results, it is clarified that the conformations of PLA and PLV in their blends are strongly influenced by intermolecular hydrogen-bonding interactions that cause their miscibility at the molecular level.

Biopolymers↗

PubMed1984

The refined 2.2-A (0.22-nm) X-ray crystal structure of the ternary complex formed by bovine trypsinogen, valine-valine and the Arg15 analogue of bovine pancreatic trypsin inhibitor.

Large orthorhombic crystals of the complex formed by bovine trypsinogen and a semisynthetic homologous bovine pancreatic trypsin inhibitor with the reactive-site lysine residue replaced by an arginine residue [( Arg15]PTI) have been obtained which are isomorphous with the crystals of PTI-trypsinogen [Bode, W., Schwager, P. and Huber, R. (1978) J. Mol. Biol. 118, 99-112]. The X-ray crystal structure of the ternary complex of trypsinogen-[Arg15]PTI with the dipeptide Val-Val has been determined by X-ray data to 2.2-A (0.22-nm) resolution by means of difference Fourier methods and has been crystallographically refined to a final R-value of 0.17. Replacement of the reactive-site Lys15 by an arginine residue is accompanied in the complex by small movements of polar side groups of trypsin and enclosed solvent molecules within the specificity pocket. Only solvent molecule 414 OH which mediates the hydrogen bond interactions between Lys15 NZ and Asp189 carboxylate is expelled, thus allowing the bulkier guanidyl group to approach this carboxylate. The dipeptide Val-Val binds in the pocket accepting the Ile-Val N-terminus in trypsin. The cavity left by the CD-methyl group of Ile16 upon replacement by a valine residue is only partially filled by slight rearrangements of neighbouring peptide side chains. Part of the positive free energy change observed upon replacement of Ile-Val may allow for the maintenance of this cavity.

Animals↗

PubMed1965