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At least 19 recordsLinked to original sources
PubMed1992

Isoleucine requirements of the chicken: the effect of excess leucine and valine on the response to isoleucine.

1. Three experiments were designed to determine the response of broiler chickens to dietary isoleucine, and to quantify the antagonistic effects of excess leucine and valine on this response. 2. A dilution technique was used to measure the responses in growth rate and food intake to a range of diets differing in their isoleucine concentrations. A summit diet was formulated to contain isoleucine at 1.14 times the requirement and with leucine (1.76 times the requirement) and valine (1.87 times the requirement) at the minimum possible concentrations, given the ingredients available. A dilution mixture, devoid of protein, was formulated to correspond in all respects, other than in amino acid content, to the summit diet. These two basal diets were blended in different proportions to give a range of diets of decreasing isoleucine and protein content. 3. In experiment 1 the response was measured to isoleucine with leucine and valine remaining in the same proportion to isoleucine throughout the range of diets fed. In experiments 2 and 3, however, L-leucine and L-valine were added to the diets either singly or in combination to give 6 isoleucine concentrations and 3 ratios of each of leucine and valine to isoleucine. 4. Weight gain decreased as the isoleucine content of the diet was reduced, whereas food intake of broilers fed on the marginally deficient diets increased to a maximum and then decreased. FCE decreased curvilinearly as the isoleucine concentration in the food decreased, reflecting a concomitant change in the fat content of the broilers. 5. It is possible that the amount of dietary isoleucine assumed to be available to the broilers in these experiments was overestimated by hydrolysing the food samples for 72 h, and the doubt thus created makes an estimate of the efficiency of retention of isoleucine suspect. 6. Excess valine had no effect on the response to isoleucine, whereas an increase in the leucine to isoleucine ratio depressed food intake and hence weight gain, but only at the lowest concentrations of isoleucine. 7. If the food content of isoleucine is sufficient to meet the requirements of the broiler, relatively large excesses of leucine, of valine, or of both will not depress growth.

Animal Feed↗
PubMed1976

Effect of intravenous L-isoleucine infusion upon concentration of free isoleucine in milk.

The growth of Streptococcus agalactiae in milk is inhibited by elevated free isoleucine. Free amino acid concentrations in both plasma and milk from three lactating dairy cows were studied after intravenous infusions of L-isoleucine at 62, 300, 380, and 840 mumol/kg of body weight. Free isoleucine was lower in milk than in plasma. The concentration of free isoleucine in plasma increased after infusions of isoleucine at the three higher amounts. The highest concentration of free isoleucine in milk measured was 1.5 mumol/100 ml of skin milk. This was observed after infusion of isoleucine for 12 h at 380 mumol/kg of body weight. Free isoleucine in both plasma and milk dropped to the preinfusion concentrations a short time after the isoleucine infusions were stopped. When relatively large quantities of isoleucine were infused into the blood of cows, free isoleucine in blood increased as much as twofold. The source of free isoleucine in milk appeared to be free isoleucine in plasma, but isoleucine in milk only reached concentrations that would give about 50% of the growth inhibition of S. agalactiae obtainable with isoleucine in vitro. It would be difficult to elevate free isoleucine in milk by dietary manipulation sufficiently to inhibit S. agalactiae.

Amino Acids↗
PubMed1985

Molecular forms of peptide histidine isoleucine-like immunoreactivity in the gastrointestinal tract. Nonequimolar levels of peptide histidine isoleucine and vasoactive intestinal peptide in the stomach explained by the presence of a big peptide histidine isoleucine-like molecule.

Regional specific antibodies and chromatography were used to analyze the distributions and molecular forms of peptide histidine isoleucine (PHI) and vasoactive intestinal peptide (VIP) in the porcine intestine. Both peptides were present along the entire length of the intestine, the highest concentrations occurring in the colon. Concentrations of PHI immunoreactivity, measured with three different antisera, and VIP immunoreactivity were approximately equal in all parts of the gastrointestinal tract except in the stomach. In the stomach, the concentration of PHI immunoreactivity, measured with the N-terminally directed antibody R8403, although equal to the corresponding VIP concentration, was two to four times higher than the PHI immunoreactivity detected with the two C-terminally directed PHI antisera T33 and T41. Chromatographic analysis on Sephadex G-50 superfine of gastric extracts revealed only one VIP immunoreactive peak that eluted in the same position as the porcine VIP standard, at Kav 0.53. A PHI immunoreactive peak was also detected with the C-terminally directed PHI antisera in the same position as porcine PHI standard. However, with the N-terminally directed PHI antiserum R8403, an additional PHI immunoreactive peak was detected in gastric extracts constituting the predominant form present, and this peak eluted earlier at Kav 0.37. The PHI immunoreactive material that eluted earlier was present in the rest of the intestine in only small amounts. As VIP and PHI are believed to be derived from a common precursor, it is suggested that in the stomach the posttranslational enzymic processing of the precursor is different from that in the other parts of the intestine.

Animals↗
PubMed1982

[Absorption and utilization of amino acids infused into the cecum of growing pigs. 1. Measurement of N-balance for utilization of lysine and isoleucine; isoleucine requirement for growing pigs].

In N-balance experiments with growing pigs (40-60 kg live weight) investigations were made whether lysine or isoleucine that is infused into the caecum can be absorbed there and to what extent these amino acids in that case can be utilised by the animal for protein synthesis. The pigs either received basic rations with insufficient lysine or isoleucine resp. (negative control group) or the amounts of lysine and isoleucine lacking to meet the requirement were supplemented with the feed (positive control group) or continuously infused into the caecum with the help of caecal infusion cannulae (test group). In the experiments with lysine the animals in the negative control group and in the test group showed considerably lower N-balances than the positive control group. There were no differences as regards the apparent digestibility of lysine between the positive control group and the test group. The urine of the test group contained distinctly more NH3. This shows clearly that lysine that is infused into the caecum cannot be utilised by the pigs, it is, on the contrary, microbially decomposed, the nitrogen is chiefly absorbed as NH3 and excreted in urine. As regards isoleucine, the deficit brought about with the basic ration was insufficient in order to achieve significant differences between the N-balance values of the groups so that unambiguous statements on the absorption and utilisation of isoleucine infused into the caecum cannot be made. Concerning apparent digestibility of isoleucine and the NH3 content of the urine, the results of the isoleucine experiments were similar to those in the lysine experiments. According to our N-balance experiments the isoleucine requirement of pigs indicated in relevant literature as 5.6 g/kg dry matter of the feed is by far too high. It should be limited to 3.5 or a maximum of 4.0 g isoleucine per kg dry matter of the feed.

Ammonia↗
PubMed1971

Isoleucine hydroxamate, an isoleucine antagonist.

Isoleucine hydroxamate (Ile.Hdx) was found to inhibit the growth of Serratia marcescens and to antagonize isoleucine. At a low concentration of Ile.Hdx, at which the growth of the wild strain was completely inhibited, the growth of an isoleucine auxotroph was not inhibited in the medium containing a limiting amount of d-threonine as the isoleucine source. At a higher concentration, this antagonist exhibited a considerable inhibitory effect on the growth of the auxotroph. Ile.Hdx showed the same inhibitory effect as isoleucine on l-threonine dehydratase activity at the concentrations 10 times those of isoleucine. Ile.Hdx caused also derepression of isoleucine-valine biosynthetic enzymes and the derepression was overcome by isoleucine. These results indicate the Ile.Hdx causes growth inhibition by its effects on isoleucine metabolism.

Chemical Phenomena↗
PubMed1975

Inhibition of Escherichia coli isoleucine biosynthesis by isoleucine tetrazole.

Growth of a derivative of Escherichia coli K-10 was strongly inhibited by 2 times 10(-4) M L-5(1-amino-2-methylbutyl)-tetrazole (isoleucine tetrazole). Growth inhibition was reversed by isoleucine, threonine, glycyl-L-isoleucine, or glycyl-L-threonine, and, in a valine-resistant mutant, by L-valine. Partial reversal of growth inhibiton was effected by L-leucine, L-methionine, or L-homoserine. The tetrazole inhibited the activity of the biosynthetic threonine deaminase (EC 4.2.1.16 L-threonine hydrolyase [deaminating]), the inhibition being relieved by L-valine. The tetrazole also inhibited isoleucyl-transfer ribonucleic acid (tRNA) synthetase (EC 6.1.1.5 L-isoleucine: tRNA ligase [adenosine monophosphate]), but was without effect on the activities of alpha-isopropylmalate synthetase or acetohydroxy acid synthetase. One class of isoleucine tetrazole-resistant mutants produced biosynthetic threonine deaminases which were no longer subject to feedback inhibition by either isoleucine or the tetrazole.

2-Isopropylmalate Synthase↗
PubMed1988

Microbial synthesis of L-[15N]leucine L-[15N]isoleucine, and L-[3-13C]-and L-[3'-13C]isoleucines studied by nuclear magnetic resonance and gas chromatography-mass spectrometry.

The preparation of leucine and isoleucine labeled with 15N and of site-specific 13C-labeled isoleucines is described. This method is based on the induction of the biosynthetic pathways specific for branched chain amino acids in glutamic acid producing bacteria, and controlled provision of stable isotope labeled precursors. Corynebacterium glutamicum (ATCC 13032), a glutamic acid overproducer, was incubated in leucine production medium which consisted of a basal medium supplemented with [15N]ammonium sulfate, glucose, and sodium alpha-ketoisocaproate. production of L-[15N]leucine reached 138 mumol/ml at an isotopic efficiency of 90%. It was purified and checked by proton NMR and GC-MS. The electron impact (EI) spectrum showed 95 atom% enrichment. The cultivation of C. glutamicum in a similar medium containing alpha-ketobutyrate yielded L-[15N]isoleucine at a concentration of 120 mumol/ml. The GC-MS EI and chemical ionization (CI) spectra confirmed enrichment of 96 atom% 15N as that of the labeled precursors. The biosynthesis of L-[13C]isoleucine was carried out by induced cells which were transferred to a similar medium in which [2-13C]- or [3-13C]pyruvic acid replaced glucose. 13C NMR of the product isoleucine revealed single-site enrichment at C-3 or at C-3' respective to the precursor [13C]pyruvate; i.e., C-3 was labeled from [2-13C]pyruvate and C-3' from [3-13C]pyruvate. Mass spectrometric analysis confirmed that all molecules were labeled only in one carbon. This site-specific incorporation of [13C]pyruvate is contrasted with the labeling pattern obtained when producing cells were supplied with [2-13C]acetate, instead of pyruvate, when most label was incorporated into carbons 3 and 3' of the same isoleucine molecule.

Actinomycetales↗
PubMedDate not supplied

Correlation between the concentration of isoleucine transfer RNA and the isoleucine content of hemoglobin in rabbit and sheep reticulocytes.

A correlation has been found between the concentration of isoleucine tRNA in reticulocytes and isoleucine content of rabbit and sheep hemoglobins: in rabbit reticulocytes, which synthesize a hemoglobin containing 8 residues of isoleucine per molecule, the isoleucine accepting activity is more than twice as high as in sheep reticulocytes, which produce a hemoglobin devoid of isoleucine.

Animals↗
PubMed1990

Nonprotein amino acid furanomycin, unlike isoleucine in chemical structure, is charged to isoleucine tRNA by isoleucyl-tRNA synthetase and incorporated into protein.

Nonprotein amino acid furanomycin was found to bind with Escherichia coli isoleucyl-tRNA synthetase (IleRS) almost as tightly as the substrate L-isoleucine. The conformation of furanomycin bound to the enzyme was determined by NMR analyses including the transferred nuclear Overhauser effect method. The conformation of IleRS-bound furanomycin was similar to that of L-isoleucine, although the chemical structure of furanomycin is unlike that of L-isoleucine. By E. coli IleRS, E. coli tRNAIle was charged with furanomycin as efficiently as with L-isoleucine. Furthermore, furanomycyl-tRNAIle was bound to polypeptide chain elongation factor Tu as tightly as isoleucyl-tRNAIle. Furanomycin was found to be incorporated into beta-lactamase precursor by in vitro protein biosynthesis. A newly designed amino acid will probably be incorporated into proteins, provided that the new amino acid takes a similar conformation as a protein-constituting amino acid in the active site of an aminoacyl-tRNA synthetase.

Amino Acids↗
PubMed1972

Isoleucine and valine metabolism in Escherichia coli. XIX. Inhibition of isoleucine biosynthesis by glycyl-leucine.

The inhibition of growth of the K-12 strain of Escherichia coli by glycyl-l-leucine observed originally by Simmonds and co-workers was investigated. The inhibition was reversed by isoleucine and those precursors of isoleucine beyond threonine in the biosynthetic pathway. Threonine reversed the inhibition poorly. With heavy cell suspensions, the inhibition was transient: the onset of growth followed the disappearance of the dipeptide from the medium and the appearance of glycine and leucine. Glycyl-leucine was shown to be an inhibitor of threonine deaminase (EC 4.2.1.16 l-threonine hydro-lyase [deaminating]). One kind of glycyl-leucine-resistant mutant had a threonine deaminase that was resistant to isoleucine and glycyl-leucine inhibition. The pattern of glycyl-leucine inhibition is compared with those of inhibition by isoleucine and by the weaker inhibitors leucine and valine.

Acylation↗
PubMed1977

Pathway for isoleucine formation form pyruvate by leucine biosynthetic enzymes in leucine-accumulating isoleucine revertants of Serratia marcescens.

Leaky revertants isolated from isoleucine auxotrophs of Serratia marcescens mutant resistant to alpha-aminobutyric acid were previously reported to accumulate leucine in the medium, due to the absence of both feedback inhibition and repression of leucine biosynthesis. Growth of the revertant was accelerated by pyruvate, D(-)-citramalate, citraconate, and alpha-ketobutyrate, but not by threonine. Extracts of the revertant exhibited high activities of pyruvate-dependent coenzyme A liberation from acetyl-coenzyme A, hydration of citraconate, and conversion of citraconate to alpha-ketobutyrate, but showed no threonine-deaminating activity. In the leucine-accumulating revertants the above three activities were not affected by leucine, but in the wild strain and other revertants accumulating no leucine all or one of these activities was controlled by leucine. A leucine auxotroph isolated from the leucine-accumulating revertant showed isoleucine auxotrophy as well. From these data, it is concluded that, in leucine-accumulating revertants, of S. marcescent, isoleucine, is synthesized from alpha-ketobutyrate via citramalate formed from pyruvate annd acetyl-coenzyme A by leucine biosynthetic enzymes, as a result of desensitization of alpha-isopropylmalate synthetase to feedback inhibition.

Acetyl Coenzyme A↗
PubMed1977

Enhancement of isoleucine hydroxamate-mediated growth inhibition and improvement of isoleucine-producing strains of Serratia marcescens.

Growth inhibition by isoleucine hydroxamate in Serratia marcescens was significantly enhanced by adding valine plus leucine and by using glycerol as the carbon source. Isoleucine hydroxamate-resistant mutants were isolated under conditions in which growth inhibition was enhanced. One of the mutants, strain GIHVLr2179, lacked both feedback inhibition and repression of threonine deaminase. An alpha-aminobutyric acid-resistant mutant derived from strain GIHVLr2179, strain GIHVLAr2795, produced 12 mg of isoleucine per ml in the medium containing glucose and urea as carbon and nitrogen sources (a twofold increase over prior reports). This strain had increased activities of threonine deaminase, acetohydroxy acid synthase, aspartokinase, and homoserine dehydrogenase.

Acetolactate Synthase↗
PubMed1989

Interrelation between the metabolism of L-isoleucine and L-allo-isoleucine in patients with maple syrup urine disease.

The nonprotein amino acid L-allo-isoleucine is formed endogenously in maple syrup urine disease patients from (R)-3-methyl-2-oxo-pentanoic acid. During strict metabolic balance, the plasma L-allo-isoleucine/L-isoleucine ratio correlates inversely with the residual activity of the branched-chain 2-oxoacid dehydrogenase in fibroblasts and thus constitutes a relevant in vivo parameter of the severity of the metabolic defect in MSUD patients.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed1979

Synthesis and pharmacological properties of [5-isoleucine]-, [8-isoleucine]-, and [5,8-diisoleucine]bradykinin.

Three bradykinin analogues have been synthesized in which the phenylalanine residue(s) at positions 5 and/or 8 have been substituted by isoleucine. All these analogues have weak bradykinin-like activity in isolated rat uterine smooth muscle or in rat blood pressure assay. No antagonistic activity was observed with any of these analogues. The importance of phenylalanine at positions 5 and 8 is discussed.

Amino Acid Sequence↗