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PubMed1996

Adducts to N-terminal valines in hemoglobin from butadiene metabolites.

In order to identify a hemoglobin adduct useful for monitoring of doses of butadiene metabolites, particularly the strongly genotoxic, bifunctional diepoxybutane (DEB), the reaction of DEB with valinamide, a relevant model of globin N-termini, was studied. A preliminary kinetic analysis showed that the primary reaction product of DEB with valine-N gives, as was expected, rise to a ring-closed pyrrolidine-structured compound, N,N-(2,3-dihydroxybuta-1,4-diyl)valine (PYRV), in a reaction which is fast when compared to hydrolysis of the second oxirane ring with formation of N-(2,3,4-trihydroxybutyl)valine (THBV). The ring closure is also fast when compared to the rate of formation of a cross-linked divaline product. PYRV can therefore be used as a specific marker of in vivo doses of DEB whereas THBV may be applied for the dosimetry of the metabolite (1,2-dihydroxyethyl)oxirane. The latter is formed by half-hydrolysis of DEB or oxygenation of 1,2-dihydroxy-3-butene. The N-alkyl Edman method, used for specific cleavage and gas chromatographic/mass spectrometric (GC/MS) determination of adducts to N-terminal valine in hemoglobin, could be used for measurement of THBV, as shown in alkylation experiments with blood. However, the adduct specific for DEB, PYRV, requires-due to its tertiary amine structure-other techniques. The reaction products were identified by GC/MS, PYRV by 13C and 1H NMR, and THBV because of its formation by reduction of the Schiff bases of threose and erythrose with hemoglobin.

Alkylation↗
PubMed1989

Sparrows discriminate between diets differing in valine or lysine concentrations.

White-crowned Sparrows (WCS) were given free access to pairs of semisynthetic diets that were either adequate or subadequate (25% of requirement) in valine or lysine. Within 2 to 4 days WCS chose a ratio of the paired diets that allowed them to maintain body mass or restore any losses quickly. On the initial choice days the birds transiently reduced total daily food intake (TDFI) roughly in proportion to their intake of the subadequate diet. The initial decrease of TDFI was greater and the latency in choosing an effective ratio of the paired diets was 2-3 days longer with valine than with lysine diets in well-nourished test birds. In malnourished birds fed only the subadequate test diet for 3 days, valine-deficient birds increased TDFI and body mass more promptly than did lysine-deficient birds when offered a choice of adequate and subadequate diets. The form of the test amino acid (CAA = crystalline, PB = protein-bound) had little effect on choice behavior, but sudden transfer of WCS from a PB acclimation diet to test diets with a large total CAA concentration increased the latency of effective choice by 2-3 days. A brief acclimation (2-3 days) to a CAA diet precludes any bias between nutritionally equivalent CAA and PB diets. The small differences in choice dynamics between valine and lysine and between dietary forms may help to identify mechanisms involved in food choice but are probably ecologically insignificant to free-living WCS. These birds are very adept at selecting diets that satisfy their amino acid requirements.

Animals↗
PubMed1986

Role of uptake of [14C]valine into protein in the development of tolerance to diisopropylphosphorofluoridate (DFP) toxicity.

In a subchronic toxicity study male Sprague-Dawley rats were daily treated with diisopropylphosphorofluoridate (DFP) (0.5 mg/kg, sc) for 14 days. Maximum signs of anticholinesterase toxicity were observed during Days 4 and 5 comparable to those seen 10-15 min following a single sublethal dosage (1.5 mg DFP/kg, sc). Signs disappeared after Days 6-7 of exposure and rats became apparently normal during the remainder of the treatment period. Significant hypothermia was seen following the second to fifth doses with maximum effect after the fifth injection. Subsequent injections of DFP did not cause any reduction in temperature. Incorporation of [14C]valine was measured 24 hr after the 5th and 14th injections of DFP, at a time when body temperature had recovered to control values. The rate of in vivo incorporation of [14C]valine was measured 0.5, 1.0, and 2.0 hr after a subcutaneous injection of L-[1-14C]valine at a dose of 5 microCi/mmol/100 g body wt. After five injections the rate of L-[1-14C]valine uptake into the free amino acid pool and the incorporation into the protein bound pool was significantly (p less than 0.01) reduced in discrete brain regions, liver, kidney, and skeletal muscles. At the end of the 14-day treatment, protein synthesis in all the skeletal muscles tested had recovered completely (p greater than 0.01) to the values of nontreated control animals. In brain, liver, and kidney, however, no recovery was seen during this period. The recovery of protein synthesis in skeletal muscle may be one of the mechanisms that lead to tolerance development during prolonged administration of subacute concentrations of DFP.

Acetylcholinesterase↗
PubMed1995

Regulation of expression of the valine (branched-chain amino acid) dehydrogenase-encoding gene from Streptomyces coelicolor.

Expression of the Streptomyces coelicolor (Sc) valine (branched-chain amino acid) dehydrogenase-encoding gene (vdh) is regulated by valine, glucose and NH+4 at the transcriptional level. The results of assays for the level of accumulated vdh mRNA in the Sc J802 strain by primer extension experiments and for the level of catechol dioxygenase (XylE) activity in Sc J802 (vdh::xylE) transformants show that transcription of the vdh gene is induced approx. 2.5-fold by valine, as compared to asparagine as the sole nitrogen source in the presence of glucose as carbon source. Valine induction is repressed by glucose, as compared to glycerol as the carbon source, and by NH+4. Glucose catabolite repression is relieved in Sc M480, a glucose kinase (glkA) deletion mutant. This suggests that glucose repression of vdh and carbohydrate metabolism are due to the same mechanism in Sc, which involves glucose kinase.

Amino Acid Oxidoreductases↗
PubMed1995

Structural identification of valine hydroperoxides and hydroxides on radical-damaged amino acid, peptide, and protein molecules.

We have previously demonstrated the formation of two reactive moieties on proteins during free radical attack: hydroperoxides, and 3,4-dihydroxyphenylalanine (DOPA). Here we have undertaken the structural elucidation of the hydroperoxides of valine, the amino acid which is most susceptible to peroxidation. Exposure of L-valine to free radicals generated by radiolysis in an oxygen-saturated system produced three valine hydroperoxides. Upon treatment with sodium borohydride these were reduced to their corresponding hydroxides, which can be separated and purified by high performance liquid chromatography (HPLC). Based on spectroscopic data from high resolution chemical ionization (CI) mass spectrometry (MS), electrospray (ES) MS, electron impact (EI) MS, proton (1H) nuclear magnetic resonance (NMR) and carbon-13 (13C) NMR studies, the three valine hydroxides have been identified as beta-hydroxyvaline [(2S)-2-amino-3-hydroxy-3-methyl-butanoic acid], (2S,3S)-gamma-hydroxyvaline [(2S,3S)-2-amino-3-hydroxymethyl-butanoic acid], and (2S,3R)-gamma-hydroxyvaline [(2S,3R)-2-amino-3-hydroxymethyl-butanoic acid]. HPLC analysis of O-phthaldialdehyde (OPA) derivatives of the hydroxyvalines provides a sensitive and accurate method for quantitative measurement. This method enabled hydroxyvalines to be detected in the hydrolysates of a tripeptide (glutamyl-valinyl-phenylalanine) and a protein (bovine serum albumin) that had been gamma-radiolysed and treated with sodium borohydride. Hydroxyvaline may be useful as a marker in studying protein oxidation in some biological systems under oxidative stress.

Amino Acids↗
PubMed1993

Acetohydroxy acid synthase and threonine deaminase activities, and the biosynthesis of isoleucine-leucine-valine in Streptococcus bovis.

Acetohydroxy acid synthase (AHAS) and threonine deaminase (TD) activities were found in Streptococcus bovis and shown to be involved in the biosynthesis of the branched chain amino acids isoleucine, leucine and valine. Apparent lack of repression of AHAS synthesis by the end-products and reduced sensitivity of S. bovis growth to analogues of the branched chain amino acids suggested that secretion of isoleucine, leucine and valine in the growth medium may be a consequence of the regulatory features of AHAS. A glycyl-leucine-resistant mutant with reduced TD activity secreted a reduced amount of isoleucine and an increased amount of valine, which might be a result of the reduced rate of synthesis of the isoleucine precursor alpha-ketobutyrate and of a consequent preferential carbon flow through the valine branch of the pathway.

Acetolactate Synthase↗
PubMedDate not supplied

The effect of a valine-rich diet on intestinal adaptation to massive small bowel resection in the rat.

BACKGROUND/PURPOSE: Recently, valine, which is one of the branched chain amino acids, has been reported to enhance liver regeneration after hepatectomy in the rat. The aim of this study was to investigate the effect of enteral valine supplementation on intestinal adaptation. MATERIALS/METHODS: Seven-week-old male Lewis rats underwent a 90% small bowel resection. The rats were randomly divided into two groups: group V (valine-rich diet) and group S (standard rat chow), according to the diet. The rats were sacrificed at the operation day and on postoperative days (POD) 7, 14, 30, and 60. The metrics were body weight (BW), blood amino acids, urine organic acids, and morphology of the residual small intestine. RESULTS: The BW and the intestinal wet weight, jejunal crypt depth, and proliferating cell nuclear antigen-positive cells in group V at POD 7 were significantly higher than those values in group S, while those in group V at POD 30 and 60 were smaller than those in group S. The urine methylmalonic acid (MMA) level in group V at POD 30 and 60 was much higher than in group S. CONCLUSION: Valine enhanced intestinal adaptation after massive small bowel resection in the acute phase. However, the long-term supplementation disturbed intestinal adaptation, which might be due to the high production of MMA.

Animals↗
PubMed1977

Effect of different concentrations of dl-isoleucine, dl-valine, and dl-alanine on growth and sporulation in Fusarium oxysporum f. udum (Butl.) Sn. et H.

D1-alanine and dl-valine, when added as an extra nitrogen for fortifying the already present inorganic nitrogen source, actually acted as growth retardant for F. oxysporum f. udum (Butl.) Sn. et H. Sporulation of microconidia was indifferently affected by these two amino acids. DI-valine stimulated microconidial formation in young cultures only. In both young and old cultures the lowest concentration of dl-valine depressed macronidial sporulation. In old cultures the lowest concentration of valine stimulated chlamydospore differentiation rapidly, higher concentrations being less effective. D1-alanine, as an additional nitrogen source, depressed both macro- and microconidal sporulation. It did not even invigorate chlamydospore formation. D1-isoleucine, on the other hand, belongs to the category of growth promoters and profuse and stimulative sporulators of macro- and microconidia. This pathogen needs very specific and preferential doses of the three amino acids, if these are used as a booster in addition to the already present nitrogen source. The response, both in terms of mycelial growth and sporulation of the three spore forms, was also conditioned by the age of the culture.

Alanine↗
PubMed1998

Determination of delta13C values of valine in protein hydrolysate by gas chromatography-combustion isotope ratio mass spectrometry.

A gas chromatographic-combustion isotope ratio mass spectrometric (GC-C-IRMS) method for the determination of [1-13C]valine enrichments in protein hydrolysates is described. Using a quick derivatization method, delta13C values of the N-methoxycarbonyl methyl ester of valine can be determined from baseline separated GC peaks. Evaluation studies with respect to precision, accuracy, linearity, reduction capacity of the CuO combustion furnace and isotope dilution as a result of derivatization, showed that our GC-C-IRMS system allows robust measurement of enrichments of [1-13C]valine in the range 0 to 1.5 MPE (S.D.+/-0.01 MPE, n=3). Therefore this method is suited to determine fractional synthetic rates (FSRs) of proteins as low as one-tenth of the FSR of human albumin, in studies using a primed, continuous (6 h) infusion with [1-13C]valine plasma enrichments of approximately 15 MPE and an hourly sampling schedule.

Carbon Isotopes↗
PubMed1998

Comparison of ethylene, propylene and styrene 7,8-oxide in vitro adduct formation on N-terminal valine in human haemoglobin and on N-7-guanine in human DNA.

Epoxides react at various nucleophilic sites in macromolecules such as haemoglobin and DNA. To study the reaction rate constants of ethylene oxide (EO), propylene oxide (PO) and styrene 7,8-oxide (SO) towards two of these positions, i.e., the N-terminal valine in haemoglobin and N-7-guanine in DNA was the central aim of this investigation. These two reactive sites are the most studied haemoglobin and DNA adducts, respectively. Further attention, therefore, was also paid to the applicability in vivo of the in vitro determined reaction constants. The determination of the second-order rate constants between EO and PO and N-terminal valine in Hb [2.7 l (mol Hb h)-1 and 1.0 l (mol Hb h)-1, respectively] were consistent with the literature values. The constants for the reaction with N-7-guanine [16x10(-3) l (mol DNA nucleotide h)-1 and 7. 7x10(-3) l (mol DNA nucleotide h)-1, respectively] were lower than previously published values, probably due to differences in the methodology used. The use of the in vitro obtained values to model the in vivo situation lead to a consistent picture for EO and PO. In contrast, for SO the in vitro ratio between the adduct formation on N-terminal valine [1.5 l (mol Hb h)-1] and N-7-guanine [0.71x10(-3) l (mol DNA nucleotide h)-1] was about two orders of magnitude greater than for the in vivo situation. This was probably due to a lower than expected reactivity of SO towards N-terminal valine in vivo. Further research is needed to elucidate whether the use of SO in vitro, contrasting with the in vivo experiments in which SO was metabolically formed from styrene, could entail an explanation for this discrepancy. Concerning the methodological part, the use of dipeptide standards to replace the alkylated globins as standard lead to an improvement of the method. Especially the commercial availability of the standards, their stability and accurately known adduct content will make them to the standards of choice in the future.

Alkenes↗
PubMed2001

Energetics of side chain packing in staphylococcal nuclease assessed by exchange of valines, isoleucines, and leucines.

To examine the importance of side chain packing to protein stability, each of the 11 leucines in staphylococcal nuclease was substituted with isoleucine and valine. The nine valines were substituted with leucine and isoleucine, while the five isoleucines, previously substituted with valine, were substituted with leucine and methionine. These substitutions conserve the hydrophobic character of these side chains but alter side chain geometry and, in some cases, size. In addition, eight threonine residues, previously substituted with valine, were substituted with isoleucine to test the importance of packing at sites normally not occupied by a hydrophobic residue. The stabilities of these 58 mutant proteins were measured by guanidine hydrochloride denaturation. To the best of our knowledge, this is the largest library of single packing mutants yet characterized. As expected, repacking stability effects are tied to the degree of side chain burial. The average energetic cost of moving a single buried methyl group was 0.9 kcal/mol, albeit with a standard deviation of 0.8 kcal/mol. This average is actually slightly greater than the value of 0.7-0.8 kcal/mol estimated for the hydrophobic transfer energy of a methylene from octanol to water. These results appear to indicate that van der Waals interactions gained from optimal packing are at least as important in stabilizing the native state of proteins as hydrophobic transfer effects.

Amino Acid Substitution↗
PubMed2001

An experimental and theoretical investigation of the chemical shielding tensors of (13)C(alpha) of alanine, valine, and leucine residues in solid peptides and in proteins in solution.

We have carried out a solid-state magic-angle sample-spinning (MAS) nuclear magnetic resonance (NMR) spectroscopic investigation of the (13)C(alpha) chemical shielding tensors of alanine, valine, and leucine residues in a series of crystalline peptides of known structure. For alanine and leucine, which are not branched at the beta-carbon, the experimental chemical shift anisotropy (CSA) spans (Omega) are large, about 30 ppm, independent of whether the residues adopt helical or sheet geometries, and are in generally good accord with Omega values calculated by using ab initio Hartree-Fock quantum chemical methods. The experimental Omegas for valine C(alpha) in two peptides (in sheet geometries) are also large and in good agreement with theoretical predictions. In contrast, the "CSAs" (Deltasigma) obtained from solution NMR data for alanine, valine, and leucine residues in proteins show major differences, with helical residues having Deltasigma values of approximately 6 ppm while sheet residues have Deltasigma approximately 27 ppm. The origins of these differences are shown to be due to the different definitions of the CSA. When defined in terms of the solution NMR CSA, the solid-state results also show small helical but large sheet CSA values. These results are of interest since they lead to the idea that only the beta-branched amino acids threonine, valine, and isoleucine can have small (static) tensor spans, Omega (in helical geometries), and that the small helical "CSAs" seen in solution NMR are overwhelmingly dominated by changes in tensor orientation, from sheet to helix. These results have important implications for solid-state NMR structural studies which utilize the CSA span, Omega, to differentiate between helical and sheet residues. Specifically, there will be only a small degree of spectral editing possible in solid proteins since the spans, Omega, for the dominant nonbranched amino acids are quite similar. Editing on the basis of Omega will, however, be very effective for many Thr, Val, and Ileu residues, which frequently have small ( approximately 15-20 ppm) helical CSA (Omega) spans.

Alanine↗
PubMed1998

Characterization of a valine-lysine thiourea cross-link on rat globin produced by carbon disulfide or N,N-diethyldithiocarbamate in vivo.

Previous in vivo studies have supported protein cross-linking by CS2 as both a mechanism of neurotoxicity and a potential biomarker of effect through the detection of a structure responsible for CS2-mediated protein cross-linking, namely, lysine-lysine thiourea. In this study, the structure of a previously uncharacterized stable protein cross-link produced by CS2 in vivo involving lysine and the N-terminal valine of globin has been determined. Rats were exposed to 50, 500, and 800 ppm CS2 for 2, 4, 8, and 13 weeks by inhalation or to 3 mmol/kg N,N-diethyldithiocarbamate administered orally on alternating days for 8 and 16 weeks. Acid hydrolysis, using 6 N HCl, of globin from control and exposed rats caused cyclization of the valine-lysine thiourea cross-link in treated rats to isopropyl norleucyl thiohydantoin. The hydrolysate was separated by size-exclusion chromatography, and the fraction that coeluted with the synthetic deuterated isopropyl norleucyl thiohydantoin internal standard was derivatized with 3-[4'-(ethylene-N,N, N-trimethylamino)phenyl]-2-isothiocyanate and analyzed by liquid chromatography/tandem mass spectrometry using selected reaction monitoring detection. Derivatized isopropyl norleucyl thiohydantoin obtained from CS2-treated rats displayed a cumulative dose response and was detectable at the lowest exposure (50 ppm, 2 weeks) at levels of approximately 50 pmol/g of globin. N, N-Diethyldithiocarbamate-treated rats, but not controls, also contained a CS2-generated valine-lysine thiourea cross-link on globin. In vitro incubation of human hemoglobin with either CS2 or N, N-diethyldithiocarbamate also resulted in the formation of CS2-generated valine-lysine thiourea. These observations demonstrate the potential of thiourea cross-linking involving a free amino terminus and epsilon-amino groups of lysine to accumulate in a long-lived globular protein and suggest that cross-linking of globin may provide a specific dosimeter of internal exposure for CS2 capable of assessing exposure over subchronic periods.

Animals↗
PubMed1982

Anthropometry and plasma valine, amino acids, and proteins in the nutritional assessment of hemodialysis patients.

Non-fasting plasma amino acids, proteins, anthropometric measurements, urea, and creatinine for 17 hemodialysis patients were compared with values in normal patients of similar age and sex. Values were characteristic for renal failure but with similarities to protein-energy malnutrition. Partial correlation coefficients, correcting for age and height, identified nutritional and non-nutritional factors. Plasma valine was the most correlated variable and was used to rank and group the patients. The group with valine less than 150 micrometers/liter had low values for 17 variables. Valine, isoleucine, leucine, threonine, asparagine, weight, and arm muscle circumference were interrelated and reflected malnutrition whereas fat correlated with calorie intake, and histidine and serine with protein intake. Taurine, aspartic acid, cystine, citrulline, urea, creatinine, prealbumin and retinol-binding protein were decreased in malnutrition but were higher than normal due to a loss of renal function. Fourteen variables, less affected by malnutrition, were changed by specific non-nutritional factors. Hemodialysis patients of long standing (1 to 11 years) apart from two patients with recurrent sepsis, were adequately nourished, but those on hemodialysis for less than 15 months, most of whom had previously received peritoneal dialysis, were malnourished. Malnutrition in dialysis patients was due to protein and energy deficiency enhanced by metabolic abnormalities of amino acids. Our study shows that plasma valine is interrelated with other nutritional variables and may be used to assess protein-energy malnutrition.

Adolescent↗
PubMed2001

Regulation of yeast acetohydroxyacid synthase by valine and ATP.

The first step in the common pathway for the biosynthesis of branched-chain amino acids is catalysed by acetohydroxyacid synthase (AHAS; EC 4.1.3.18). The enzyme is found in plants, fungi and bacteria, and is regulated by controls on transcription and translation, and by allosteric modulation of catalytic activity. It has long been known that the bacterial enzyme is composed of two types of subunit, and a similar arrangement has been found recently for the yeast and plant enzymes. One type of subunit contains the catalytic machinery, whereas the other has a regulatory function. Previously, we have shown [Pang and Duggleby (1999) Biochemistry 38, 5222--5231] that yeast AHAS can be reconstituted from its separately purified subunits. The reconstituted enzyme is inhibited by valine, and ATP reverses this inhibition. In the present work, we further characterize the structure and the regulatory properties of reconstituted yeast AHAS. High phosphate concentrations are required for reconstitution and it is shown that these conditions are necessary for physical association between the catalytic and regulatory subunits. It is demonstrated by CD spectral changes that ATP binds to the regulatory subunit alone, most probably as MgATP. Neither valine nor MgATP causes dissociation of the regulatory subunit from the catalytic subunit. The specificity of valine inhibition and MgATP activation are examined and it is found that the only effective analogue of either regulator of those tested is the non-hydrolysable ATP mimic, adenosine 5'-[beta,gamma-imido]triphosphate. The kinetics of regulation are studied in detail and it is shown that the activation by MgATP depends on the valine concentration in a complex manner that is consistent with a proposed quantitative model.

Acetolactate Synthase↗
PubMed1970

The effect of electrical stimulation and ouabain on the uptake and efflux of L-[U-14C] valine in chopped tissue from guinea-pig cerebral cortex.

1. Chopped tissue from guinea-pig cerebral cortex carried out an energy-dependent accumulation of l-[(14)C]valine. 2. The uptake was dependent on the extracellular concentration of Na(+) and was markedly inhibited by ouabain (20mum). The extent of the inhibition of uptake by ouabain was also Na(+)-dependent. 3. The accumulation of labelled valine was not directly dependent on the ATP and creatine phosphate contents of the slices. 4. Electrical stimulation increased the rate of [(14)C]valine uptake at first but ultimately led to a net loss of the label so that the amount of label present in the tissue was lower than in the controls. 5. The rate of loss of label during prolonged stimulation was dependent on the extracellular concentration of Na(+). 6. The efflux of labelled valine from slices preloaded at 164mm-Na(+) was studied at 164, 80 and 40mm-Na(+) with and without electrical stimulation or ouabain. 7. Lowering the Na(+) concentration or adding ouabain increased the rate of efflux. 8. Electrical stimulation had little effect on the rate of efflux at first but ultimately led to a more complete loss of label from the tissue than occurred in the control. A kinetic analysis of the efflux curves was attempted.

Adenosine Triphosphate↗
PubMed2000

Novel gain-of-function mutations of platelet glycoprotein IBalpha by valine mutagenesis in the Cys209-Cys248 disulfide loop. Functional analysis under statis and dynamic conditions.

Platelet-type von Willebrand disease is a bleeding disorder resulting from gain-of-function mutations of glycoprotein (GP) Ibalpha that increase its affinity for von Willebrand factor (vWf). The two known naturally occurring mutations, G233V and M239V, both enrich the valine content of an already valine-rich region within the Cys(209)-Cys(248) disulfide loop. We tested the effect of converting other non-valine residues in this region to valine. Of 10 mutants expressed in CHO cells as components of GP Ib-IX complexes, four displayed a gain-of-function phenotype (G233V, D235V, K237V, and M239V) based on (125)I-vWf binding and adhesion to immobilized vWf. The remainder displayed loss-of-function phenotypes. The gain-of-function mutants bound vWf spontaneously and had a heightened response to low concentrations of ristocetin or botrocetin, whereas the loss-of-function mutants bound vWf more poorly than wild-type GP Ibalpha. No distinct gain- or loss-of-function conformations were identified with conformation-sensitive antibodies. Compared with cells expressing wild-type GP Ibalpha, cells expressing the gain-of-function mutants rolled significantly more slowly over immobilized vWf under flow than wild-type cells and were able to adhere to vWf coated at lower densities. In aggregate, these data indicate that the region of GP Ibalpha bounded by Asn(226) and Ala(244) regulates the affinity for vWf.

Amino Acid Sequence↗
PubMed1985

Relationship between food consumption and energy and nitrogen utilisation by chicks given varying amounts of standard and leucine-, isoleucine- and valine-deficient diets.

The effect of different amounts of food, varying from below to above the rate of voluntary intake, was studied in chicks using a standard diet and diets containing only half the recommendation concentrations of leucine, isoleucine or valine. Irrespective of diet the body weight gain of the chicks increased with increasing food consumption. The body weight gain of chicks given the leucine-deficient diet was similar to that of chicks given the same amount of the standard diet. In contrast, the body weight gains of chicks given either the valine- or isoleucine-deficient diet were significantly less than that of chicks given the same amount of the standard diet. When the food intakes of the birds were similar the differences in body protein and water contents of the birds fed the different diets reflected differences in body weight gains, whereas body fat content was affected in the reverse manner. Retention and retention rate of dietary energy increased as food consumption increased. This was particularly evident in chicks given the isoleucine-deficient diet, followed by those given the valine-, leucine-deficient and standard diets. For all diets, the amounts of nitrogen retained and nitrogen retention rate (N retained/N consumed) increased in line with body weight gain. The metabolisable energy values of the diets were similar, except for the isoleucine-deficient diet which had a significantly higher metabolisable energy value than the standard valine-deficient diets.

Amino Acids, Essential↗