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Some amino acid systems are known to exhibit solid solution and/or co-crystal behavior upon crystallization, which significantly affects their phase diagrams and complicates the design of their purification processes. Such behaviors are observed in the l-valine/l-leucine system. In this work, the formation and stability of a 3:1 co-crystal of the two amino acids (designated as V3L) is further investigated. To accomplish the formation, liquid-assisted grinding, slurry equilibration, and sublimation experiments were performed and analyzed via HPLC and PXRD. Additionally, periodic DFT calculations were used to calculate lattice energies and determine the thermodynamics of possible solid phases. Experimental results show a clear metastability of the investigated V3L co-crystals when compared to its stable solid solution. The calculations underline the metastability and the possible formation of continuous solid solutions between l-valine and l-leucine since lattice energy differences between pure amino acids and mixed compositions are negligible. This previously unknown phase behavior can be used to assess the influence of V3L on the amino acid purification process and provides a basis for investigating similar systems with small energy differences between pure and mixed compositions in future studies. In addition, it demonstrates the particular variability of solid phases and their relationships in such simple but biologically important amino acid systems.

Detection of foodborne pathogen infection by detecting key metabolic markers is an effective measure to maintain food hygiene and safety. Therefore, the rapid, efficient, sensitive and convenient method of high-performance liquid chromatography-photodiode array (HPLC-PDA) was established and optimized to determine four key metabolic biomarkers in chicken meat infected with Salmonella Enteritidis, including L-proline (Pro), L-valine (Val), L-methionine (Met), L-leucine (Leu). The limits of detection and quantification (LOD, LOQ) for four target metabolic biomarkers were 4.50–6.5 μg/kg and 25 μg/kg, respectively. The calibration curves show a good linear relationship (R2 ≥ 0.9996). The recoveries were in the range of 80–120 %, and the relative standard deviations (RSD) were all lower than 6 %. The experimental results can be used for rapid detection of chicken meat contaminated by Salmonella Enteritidis to ensure food safety. Furthermore, the HPLC-PDA method is well applied in practice. [Display omitted] • Identification of Salmonella enteritidis infected chicken by metabolites detection. • Simultaneous determination of the key metabolites in infected chicken by HPLC-PDA. • The HPLC-PDA method compared with streak plate and RT-PCR methods. • The detection process was completed in 22 min. [ABSTRACT FROM AUTHOR]

Industrial amino acid production strains of Corynebacterium glutamicum are usually obtained by mutagenesis. However, the genetic and metabolic characteristics and the efficient synthesis mechanism of the selected mutants are unclear. The aims of this study were (1) to determine the gene transcriptional patterns and intracellular metabolite levels of an L-leucine-producing mutant C. glutamicum CP and an L-valine-producing mutant C. glutamicum XV referring to wild type, and (2) to understand the efficient synthesis mechanism of target product of these mutants. For this purpose, transcriptomic and metabolomics analyses were combined to investigate the association between intracellular patterns and product synthesis. The high intracellular level of glucose and the low intracellular level of metabolites in the central carbon metabolism meant the glucose metabolism rate of two mutants was lower than wild type. However, the increased intracellular pentose level and gene transcription in the pentose phosphate pathway (PPP) indicated that the PPP of mutants was more active. Furthermore, the mutants showed higher intracellular level of NADPH, which was mainly generated in PPP. In the specific pathway for the synthesis of L-leucine and L-valine, the transcriptional level of most genes was upregulated in the mutants. However, the transcription of transaminase C coding gene Cgl2844 was downregulated in CP but upregulated in XV. The upregulation of Cgl2844 might benefit to the synthesis of L-valine and cause the significant decrease of intracellular level of L-alanine and L-glutamate of XV. These characteristics of the mutants provided insight into changes that could be made to systematically optimize the metabolic pathways for the production of L-leucine and L-valine. [ABSTRACT FROM AUTHOR]

The leucine-to-glutamate (Leu→Glu) pathway, which metabolizes the carbon atoms of L-leucine to form L-glutamate, was studied by incubation of rat tissue segments with L-[U-14C]leucine and estimation of the [14C]glutamate formed. Metabolism of the leucine carbon chain occurs in most rat tissues, but maximal activity of the Leu→Glu pathway for glutamate formation is limited to the thoracic aorta and pancreas. In rat aorta, the Leu→Glu pathway functions to relax the underlying smooth muscle; its functions in the pancreas are unknown. This report characterizes the Leu→Glu pathway of rat pancreas and develops methods to examine its functions. Pancreatic segments effect net formation of glutamate on incubation with L-leucine, L-glutamine, or a mix of 18 other plasma amino acids at their concentrations in normal rat plasma. Glutamate formed from leucine remains mainly in the tissue, whereas that from glutamine enters the medium. The pancreatic Leu→Glu pathway uses the leucine carbons for net glutamate formation; the α-amino group is not used; the stoichiometry is as follows: 1 mol of leucine yields 2 mol of glutamate (2 leucine carbons per glutamate) plus 2 mol of CO2. Comparison of the Leu¡Glu pathway in preparations of whole pancreatic segments, isolated acini, and islets of Langerhans localizes it in the acini; relatively high activity is found in cultures of the AR42J cell line and very little in the INS-1 832/13 cell line. Pancreatic tissue glutamate concentration is homeostatically regulated in the range of ∼1-3 μmol/g wet wt. L-Valine and leucine ethyl, benzyl, and tertbutyl esters inhibit the Leu→Glu pathway without decreasing tissue total glutamate. [ABSTRACT FROM AUTHOR]

Abstract: The viscosities, η of l-alanine, l-valine and l-leucine with drug ampicillin (AMP) have been measured as a function of temperature at T =(305.15, 310.15 and 315.15)K. The viscosity data have been utilized to determine viscosity B-coefficients employing the Jones–Dole equation. The trends of variation in viscosity values of amino acids with an increase in molal concentration of AMP solutions and also with an increase in temperature have been ascribed to the solute–solvent interactions operative in the solutions. The activation parameters of viscous flow have been obtained to throw light on the mechanism of viscous flow. These parameters have been discussed in the light of ion–ion and ion–solvent interactions. [Copyright &y& Elsevier]

The article focuses on a research conducted in order to describe a detailed description of adult seasonal activity and male response to sex attractants of the scarab beetle, Phyllophaga lissopyge isolated from South America. It discusses the construction of a male capture response curve for each Phyllophaga species to illustrate the proportional capture of males with respect to pheromone treatment.

Abstract: Branched chain amino acids (BCAA) have been shown to have a general protective effect on the heart in different animal models as well as in humans. However, so far no attempt has been made to specifically elucidate their influence on arrhythmias. Our study was performed to evaluate whether an infusion of either l-leucine or l-valine in a dose of 1mgkg−1 h−1 10min before a 7-min period of left anterior descending artery occlusion followed by 15min of reperfusion, had an effect on arrhythmias measured during the reperfusion phase in the ischemia- and reperfusion-induced arrhythmias model in rats in vivo. The effect of the infusion of these substances on mean arterial blood pressure was monitored throughout the experiment. Both of the tested amino acids exhibited significant antiarrhythmic properties. l-Leucine reduced the duration of ventricular fibrillation (P <0.05) and l-valine decreased the duration of ventricular fibrillation (P <0.001) and ventricular tachycardia (P <0.05). The two amino acids were generally hypotensive. l-Valine lowered blood pressure in all phases of the experiment (P <0.05) while l-leucine lowered this parameter mainly towards the end of occlusion and reperfusion (P <0.05). In addition, 30min infusion of the amino acids in the used dose did not produce any apparent adverse histological changes that were remarkably different from control. In summary, the results of our study suggest that l-leucine and l-valine in the dose that was used attenuates arrhythmias and are hypotensive in their influence. Our findings lend support to the many ongoing investigations into the benefit of the application of l-leucine and l-valine in cardiology like their addition to cardioplegic solutions. [Copyright &y& Elsevier]

The branched chain amino acids (BCAAs), l-valine, l-leucine, and l-isoleucine, have recently been attracting much attention as their potential to be applied in various fields, including animal feed additive, cosmetics, and pharmaceuticals, increased. Strategies for developing microbial strains efficiently producing BCAAs are now in transition toward systems metabolic engineering from random mutagenesis. The metabolism and regulatory circuits of BCAA biosynthesis need to be thoroughly understood for designing system-wide metabolic engineering strategies. Here we review the current knowledge on BCAAs including their biosynthetic pathways, regulations, and export and transport systems. Recent advances in the development of BCAA production strains are also reviewed with a particular focus on l-valine production strain. At the end, the general strategies for developing BCAA overproducers by systems metabolic engineering are suggested. [ABSTRACT FROM AUTHOR]

Abstract: Solid–liquid equilibria in the system l-leucine + l-valine + water have been measured at 298K and ambient pressure. The system was shown to form solid solutions at equilibrium. The data also showed that the equilibrium composition of l-leucine in the liquid phase was only slightly affected by the presence of l-valine; whereas, the equilibrium composition of l-valine increased significantly with the addition of l-leucine. A simple thermodynamic model was used to correlate binary l-leucine + water and l-valine + water solubility data, and then to estimate nonidealities in the solid phase in the ternary system. Surprisingly, the solid solution exhibited significant nonidealities, emphasizing the need for analysis of the solid phase when ternary solubilities are measured. [Copyright &y& Elsevier]

Solid–liquid equilibria in the system l-leucine + l-valine + water have been measured at 298K and ambient pressure. The system was shown to form solid solutions at equilibrium. The data also showed that the equilibrium composition of l-leucine in the liquid phase was only slightly affected by the presence of l-valine; whereas, the equilibrium composition of l-valine increased significantly with the addition of l-leucine. A simple thermodynamic model was used to correlate binary l-leucine + water and l-valine + water solubility data, and then to estimate nonidealities in the solid phase in the ternary system. Surprisingly, the solid solution exhibited significant nonidealities, emphasizing the need for analysis of the solid phase when ternary solubilities are measured. [Copyright &y& Elsevier]

Branched-chain amino acids (L-isoleucine, L-valine, and L-leucine) are being increasingly used in sport supplements. This study evaluated toxicological and behavioral effects of L-isoleucine (Ile), L-valine (Val), and L-leucine (Leu) during a dosing study with male and female Sprague-Dawley rats. The amino acids were incorporated into a standard diet at doses equal to 1.25%, 2.5%, and 5.0% (w/w). A control group of rats received a standard diet. All diets were administered ad libitum for 13 consecutive weeks. To examine stability of any potential effects, the administration period was followed by a 5-week recovery period, during which only the standard diet was provided to all animals. No significant, dose-related effects on body weight were found in rats fed a Leu-and Ile-supplemented diet. Val mixed into a diet at 5.0% (w/w) decreased slightly, but significantly body weight gain in females, but not males. Ile (5.0% w/w) affected the urine electrolytes, protein, ketone bodies, urine glucose, and urobilinogen in both genders, yet the observed changes remained mostly within the range observed in controls. The random findings in hepatology and ophthalmology at the 13-week sacrifice were not considered toxicologically relevant to effects of the tested amino acids. No significant changes in organ weights were recorded. We estimate the no-observed-adverse-effect level (NOAEL) for Ile at 2.5% for both genders (male, 1.565 ± 0.060 g/kg/day; females, 1.646 ± 0.095 g/kg/day), Val at 5.0% for males (3.225 ± 0.135 g/kg/day) and 2.5% for females (1.853 ± 0.060 g/kg/day), and Leu at 5.0% for both genders (males, 3.333 ± 0.101 g/kg/day: females, 3.835 ± 0.257 g/kg/day). [ABSTRACT FROM AUTHOR]

Branched-chain amino acids (L-isoleucine, L-valine, and L-leucine) are being increasingly used in sport supplements. This study evaluated toxicological and behavioral effects of L-isoleucine (Ile), L-valine (Val), and L-leucine (Leu) during a dosing study with male and female Sprague-Dawley rats. The amino acids were incorporated into a standard diet at doses equal to 1.25%, 2.5%, and 5.0% (w/w). A control group of rats received a standard diet. All diets were administered ad libitum for 13 consecutive weeks. To examine stability of any potential effects, the administration period was followed by a 5-week recovery period, during which only the standard diet was provided to all animals. No significant, dose-related effects on body weight were found in rats fed a Leu-and lie-supplemented diet. Val mixed into a diet at 5.0% (w/w) decreased slightly, but significantly body weight gain in females, but not males. He (5.0% w/w) affected the urine electrolytes, protein, ketone bodies, urine glucose, and urobilinogen in both genders, yet the observed changes remained mostly within the range observed in controls. The random findings in hepatology and ophthalmology at the 13-week sacrifice were not considered toxicologically relevant to effects of the tested amino acids. No significant changes in organ weights were recorded. We estimate the no-observed-adverse-effect level (NOAEL) for He at 2.5% for both genders (male, 1.565 ± 0.060 g/kg/day; females, 1.646 ± 0.095 g/kg/day), Val at 5.0% for males (3.225 ± 0.135 g/kg/day) and 2.5% for females (1.853 ± 0.060 g/kg/day), and Leu at 5.0% for both genders (males, 3.333 ± 0.101 g/kg/day: females, 3.835 ± 0.257 g/kg/day). [ABSTRACT FROM PUBLISHER]

Apparent molar volumes of glycine, DL-α-alanine, L-valine, L-leucine, and L-phenylalanine in 0.5, 1.0, 2.0, 3.5, and 5.0 mB (mol-kg−1) aqueous solutions of glycerol have been obtained from solution densities at 25°C using precise vibrating-tube digital densimeter. The estimated partial molar volumes at infinite dilution Vo 2 have been used to obtain the corresponding transfer volumes Δtr V2 o from water to different glycerol–water mixtures. The transfer volumes are positive for glycine and DL-α-alanine, and both positive and negative for the other amino acids over the concentration range studied. Interaction coefficients have been obtained from McMillan–Mayer approach and the data have been interpreted in terms of solute–cosolute interactions. [ABSTRACT FROM AUTHOR]

The continuous administration of physiological doses of the branched-chain amino acids leucine, isoleucine, and valine (Leu-Ile-Val) to Yoshida sarcoma-bearing rats caused a significant increase in the survival time by 32% and a significant reduction of tumor size after 3 weeks of growth by 33%. The shift of the nitrogen balance to negative values during the cachectic stage was delayed but not prevented. On the average, less nitrogen (-47 mg/day) were lost by Leu-Ile-Val treated rats compared with untreated tumor-bearing animals (-91 mg N/day). It appeared that Leu-Ile-Val increased the synthesis of carcass proteins, while it left the proteolysis rate unchanged, since the excretion of urea and creatinine was unaffected by these amino acids. The daily excretion of α-ketoglutarate, which is correlated with tumor size during the early stage of growth, was decreased during the first 2 weeks by Leu-Ile-Val, but remained for a longer period on a high level than in untreated tumor bearers. The results point to an improvement of the metabolic resistance against carcass protein depletion of the tumor-bearing host by the administration of branched-chain amino acids. [ABSTRACT FROM AUTHOR]

A multienzyme system consisting of leucine dehydrogenase (EC 1.4.1.9), L-lactic dehydrogenase (EC 1.1.1.27), urease (EC 3.5.1.5), and dextran-NAD was microencapsulated within artificial cells. This system could convert ammonia and urea into essential amino acids, L-leucine, L-valine, and L-isoleucine. L-lactate acted as a cosubstrate for the regeneration of dextran-NADH. Greater concentrations of L-lactate favored the higher conversion ratios. The effects of ammonium salts and urea on reaction rate were also studied. The relative reaction rates in ammonium salts solutions were 44.6-78.8% of those in urea solutions. More than 90% of the original activity was retained when artificial cells were kept at 4°C for 6 wk. [ABSTRACT FROM AUTHOR]

L-glutamine dramatically augments insulin release evoked by L-leucine. The dynamics, specificity and environmental modifications of the insulin secretory response to the combination of L-glutamine and L-leucine were investigated. L-glutamine alone failed to stimulate proinsulin biosynthesis or insulin release in rat pancreatic islets, but augmented synthesis and secretion evoked by L-leucine. In relation to the secretory response, L-glutamine could be replaced by L-asparagine but not L-glutamate; L-leucine could be replaced by L-norvaline or L-isoleucine but not by L-valine, L-norleucine, glycine, L-serine, L-lysine, L-phenylalanine or L-arginine. The secretory response to L-leucine was rapid and biphasic, whereas the enhancing action of L-glutamine upon insulin release was progressive. The release of insulin evoked by the combination of L-leucine and L-glutamine was inhibited by antimycin A, menadione, ammonium ions, verapamil, adrenaline, and by the absence of extracellular Ca. It was increased at high carbon dioxide tension, and by glucose, theophylline and cytochalasin B. It is concluded that the enhancing action of L-glutamine upon insulin release evoked by certain amino acids represents a phenomenon dependent on the integrity of oxidative metabolism and involving essentially the same sequence of metabolic, ionic and motile events as that characterizing the process of glucose-induced insulin release. [ABSTRACT FROM AUTHOR]

Abstract: Viscosity coefficients of (l-alanine-, l-proline, l-valine, l-leucine+2.0M aqueous KCl/KNO3) solutions have been determined as a function of amino acid concentration at different temperatures: (298.15, 303.15, 308.15, 313.15, 318.15, and 323.15)K. The trends of variation of viscosity values with increase in the concentration of l-alanine, l-proline, l-valine, and l-leucine in 2.0M aqueous KCl and 2.0M aqueous KNO3 solutions, and temperature have been ascribed to the solute–solvent interactions operative in the solutions. [Copyright &y& Elsevier]