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At least 145 records · Page 8Linked to original sources
PubMed2000

Formation of L-alloisoleucine in vivo: an L-[13C]isoleucine study in man.

L-alloisoleucine (2S, 3R), a diastereomer of L-isoleucine (2S, 3S), is a normal constituent of human plasma. Considerable amounts accumulate in maple syrup urine disease, in which the branched-chain 2-oxo acid dehydrogenase step is impaired. The mechanism of L-alloisoleucine formation, however, is unclear. We addressed this issue by performing oral L-[1-13C]isoleucine loading (38 micromol/kg body wt, 50% 1-13C) in overnight-fasted healthy subjects (n = 4) and measuring the 3-h kinetics of 13C-label incorporation into L-isoleucine plasma metabolites. Compared with L-isoleucine, the time course of 13C-enrichment in the related 2-oxo acid, S-3-methyl-2-oxopentanoate, was only slightly delayed. Peak values, amounting to 18+/-4 and 17+/-3 mol percent excess, respectively, were reached within 35 and 45 min, respectively. The kinetics of 13C-enrichment in S- and R-3-methyl-2-oxopentanoate enantiomorphs were similar and linearly correlated (p << 0.001). In L-alloisoleucine, however, 13C-label accumulated only gradually and in minor amounts. Our results indicate that R-3-methyl-2-oxopentanoate is an immediate and inevitable byproduct of L-isoleucine transamination and further suggest that alloisoleucine is primarily formed via retransamination of 3-methyl-2-oxopenanoate in vivo.

Adult↗
PubMed1999

Effects of a feedback-resistant aspartokinase III gene on L-isoleucine production in Escherichia coli K-12.

An L-isoleucine-overproducing recombinant strain of E. coli, TVD5, was also found to overproduce L-valine. The L-isoleucine productivity of TVD5 was markedly decreased by addition of L-lysine to the medium. Introduction of a gene encoding feedback-resistant aspartokinase III increased L-isoleucine productivity and decreased L-valine by-production. The resulting strain accumulated 12 g/l L-isoleucine from 40 g/l glucose, and suppression of L-isoleucine productivity by L-lysine was relieved.

Aspartate Kinase↗
PubMed1992

15N-leucine and 15N-isoleucine isotope dilution techniques versus the 15N-isotope dilution technique for determining the recovery of endogenous protein and amino acids in digesta collected from the distal ileum in pigs.

Twelve gilts, with an average initial BW of 38 kg, were fitted with simple T-cannulas at the distal ileum and two catheters in the external jugular veins. The animals were fed twice daily (0800 and 2000) 700 g of one of four diets containing either soybean meal, canola meal, wheat, or barley as the sole protein source. 15N-leucine was infused continuously for 9 d at a rate of 40 mg/kg of BW daily via one of the jugular catheters. Blood samples were taken during feeding. Ileal digesta samples were collected continuously for 24 h on d 7 and 9 of the infusion period. 15N-enrichment excess in leucine and isoleucine in the trichloroacetic acid (TCA)-soluble fraction of blood and in digesta were measured using single-ion monitoring gas chromatography-mass spectrometry. Assuming that the 15N-enrichment excess in leucine and isoleucine in the TCA-soluble fraction of the blood is similar to that in endogenous protein secreted into the digestive tract and that the amino acid composition of endogenous protein is constant, the contribution of endogenous to total protein in ileal digesta was calculated using the 15N-isotope dilution technique for leucine and isoleucine, respectively. These contributions were much smaller for the 15N-leucine than for the 15N-isoleucine isotope dilution technique: 7.1 to 11.0 vs 21.8 to 24.9 g of protein/kg of DM intake. The values obtained with the 15N-isoleucine isotope dilution technique were close to those obtained with the 15N-isotope dilution technique as described in a previous publication.

Amino Acids↗
PubMed1975

Isoleucine metabolism by leukemic and normal human leukocytes in relation to cell maturity and type.

The metabolism of an essential amino acid, isoleucine, by human leukemic and gradient-separated normal human leukocytes of various types and maturity was studied. Blood leukocytes were isolated and incubated with (U-14C) isoleucine. Separation of metabolic intermediates was accomplished by sequential extraction. The rate of isoleucine incorporation into protein by immature cells from untreated patients with acute leukemia (15.9 plus or minus 2.4 nmoles/hr per 10-8 leukocytes) was considerably higher than the rates of incorporation by mature neutrophils (3.2 plus or minus 0.5 nmoles/hr per 10-8 leukocytes), lymphocytes (7.7 plus or minus 1.2 nmoles/hr per 10-8 leukocytes), and eosinophils (6.2 plus or minus 1.3 nmoles/hr per 10-8 leukocytes). Those cell preparations with more blast cells had higher rates of protein synthesis. In addition, those cells with greater thymidine incorporation had higher rates of protein synthesis. The leukocytes both oxidized isoleucine and incorporated it into cell isoleucine and incorporated it into cell lipid. The rates of these metabolic processes were characteristic for various types and maturity of leukocytes. This study demonstrates a relationship of rate of protein synthesis to leukocyte immaturity. This relationship is maintained in neoplastic leukocytes. It suggests that the requirement of the mitotic process for newly synthesized protein is greater than that for the elaboration of the protein products of the mature leukocyte.

Blood Proteins↗
PubMed2006

Dietary branched-chain amino acid valine, isoleucine and leucine requirements of fingerling Indian major carp, Cirrhinus mrigala (Hamilton).

Three 8-week growth experiments were conducted to quantify the requirements of the fingerling Cirrhinus mrigala for the dietary branched-chain amino acids valine (experiment 1), isoleucine (experiment 2) and leucine (experiment 3). Six isonitrogenous (400 g/kg) and isoenergetic (17.90 kJ/g) test diets were formulated with a gradation of 2.5 g/kg for each test amino acid, valine (7.5-20 g/kg), isoleucine (5.0-17.5 g/kg) and leucine (7.5-20 g/kg), and fed to randomly stocked fish in circular troughs. In experiment 1, the maximum weight gain (312 %), best feed conversion ratio (FCR; 1.45) and best protein efficiency ratio (PER; 1.72) were obtained in fish fed 15.0 g dietary valine/kg. In experiment 2, the highest weight gain (317 %), best FCR (1.47) and best PER (1.70) were recorded at 12.5 g dietary isoleucine/kg, and in experiment 3, the highest weight gain (308 %), best FCR (1.46) and best PER (1.71) were noted at 15.0 g dietary leucine/kg. A quadratic regression analysis of weight gain, FCR and PER data showed an optimum requirement at 15.9, 15.0 and 14.8 g/kg for valine, 13.2, 12.3 and 12.1 g/kg for isoleucine and 15.6, 15.4 and 15.1 g/kg for leucine in dry diets. Low body moisture and higher protein were noted in fish fed diets containing 15.5, 12.5 and 15.0 g valine, isoleucine and leucine per kg, respectively. Body fat increased with increasing levels of the branched-chain amino acids. On the basis of a regression analysis of growth data, it is recommended that a diet for C. mrigala should contain valine at 15.2, isoleucine at 12.6 and leucine at 15.4 g/kg dry diet, corresponding to 38.0, 31.5 and 38.5 g/kg dietary protein, respectively.

Amino Acids, Branched-Chain↗
PubMedDate not supplied

[Separation of a mixture of L-isoleucine and L-leucine].

The conditions of L-leucine and L-isoleucine esterification were investigated. It was found that chromatographically homogeneous L-isoleucine and L-leucine could be isolated from their mixture during its incomplete esterification. As a result, L-leucine transformed into L-leucine and ester chlorohydrate L-isoleucine into L-isoleucine chlorohydrate. By means of further neutralization of the reaction mixture L-isoleucine with a 80-85% yield was obtained, and with the aid of L-leucine ester hydrolysis L-leucine with a 80-85% yield was produced. The content of the major amino acid following its crystallization from the water-ethanol mixture was 99%.

Chromatography, Thin Layer↗
PubMed1991

Evidence that some preganglionic sympathetic neurons in the rat contain vasoactive intestinal peptide- or peptide histidine isoleucine amide-like immunoreactivities.

Physiological studies have established that preganglionic sympathetic nerve fibers innervating the rat superior cervical ganglion release a second transmitter, in addition to acetylcholine. Based on pharmacological and histochemical investigations, possible candidates for this non-cholinergic neurotransmitter include vasoactive intestinal peptide and peptide histidine isoleucine amide. For example, previous immunohistochemical studies have demonstrated that antisera raised against both of these peptides stain neural processes in the rat preganglionic cervical sympathetic trunk and in the superior cervical ganglion. In the present study, it was found that, when the cervical sympathetic trunk was ligated, vasoactive intestinal peptide- and peptide histidine isoleucine amide-like immunoreactivities built up on both sides of the ligature. In addition, examination of the thoracic spinal cord in colchicine-treated animals revealed vasoactive intestinal peptide- and peptide histidine isoleucine amide-like immunoreactivies in neuronal cell bodies in the intermediolateral cell column and in the region of the lateral funiculus adjacent to it. In a second group of animals in which retrograde tracing techniques were used, these two regions of the spinal cord were shown to contain most of the cell bodies of the preganglionic neurons that project to the superior cervical ganglion. Smaller numbers of retrogradely labeled neurons were found dorsal to the central canal and in the nucleus intercalatus. When either vasoactive intestinal peptide- or peptide histidine isoleucine amide-like immunostaining and retrograde labeling were examined in the same animals, double-labeled neurons were found in the intermediolateral cell column and in the lateral funiculus. These data demonstrate that vasoactive intestinal peptide- and peptide histidine amide-like immunoreactivities are present in certain of the preganglionic neurons that project to the superior cervical ganglion, supporting the hypothesis that vasoactive intestinal peptide and peptide histidine isoleucine amide are released in the ganglion when these preganglionic neurons are activated.

Animals↗
PubMed1994

Somatostatin, galanin and peptide histidine isoleucine in the newborn and adult human trigeminal ganglion and spinal nucleus: immunohistochemistry, neuronal morphometry and colocalization with substance P.

By means of indirect immunofluorescence the neuropeptides somatostatin, galanin and peptide histidine isoleucine were localized in cell bodies, nerve fibres and terminal-like elements in the ganglion and spinal nucleus of the human trigeminal nerve in perinatal and adult ages. No immunoreactivity to vasoactive intestinal polypeptide was observed. In the gasserian ganglion somatostatin-, galanin- and peptide histidine isoleucine-containing neurons and nerve fibres occurred frequently in pre- and full-term newborns, but were scarce to absent in adults. Somatostatin- and galanin-positive pericellular basket-like structures around non-immunoreactive perikarya were observed in newborn specimens. Immunoreactivity to somatostatin, galanin and peptide histidine isoleucine labelled nerve fibers and punctate and felt-like nerve terminals in the pars interpolaris and subnucleus caudalis of the spinal trigeminal nucleus, with immunostaining and distribution patterns characteristic for each peptide. In addition, somatostatin-containing neuronal cell bodies frequently were detected. At variance with those containing somatostatin, the number of galanin- and peptide histidine isoleucine-like immunoreactive elements were dramatically reduced in the adult tissue compared to the newborn one. Double immunostaining revealed that each of the three peptides partially colocalizes with substance P, the degree of coexistence being very low for somatostatin/substance P and high for galanin/substance P and peptide histidine isoleucine/substance P both in the gasserian ganglion and in the spinal nucleus. The results obtained suggest that somatostatin, galanin and peptide histidine isoleucine may play functional roles in primary sensory neurons and at the first synaptic level of the human trigeminal sensory system.

Aged↗
PubMed1985

Reversal of chlorsulfuron-induced inhibition of mitotic entry by isoleucine and valine.

Pea (Pisum sativum L. cv Alaska) root tips were excised and cultured aseptically in White's medium. Cultures were treated immediately or after a 24 hour equilibration time with 28 nanomolar chlorsulfuron plus isoleucine and valine (each 0.1 millimolar), isoleucine and valine, or untreated. The percentage of mitotic figures in untreated control roots sampled immediately after excision showed a transitory drop and recovery within 24 hours (an excision effect). In chlorsulfuron-treated roots, the percentage of mitotic figures did not recover. In roots treated with chlorsulfuron plus isoleucine and valine, a complete recovery did occur. If roots were treated with chlorsulfuron 24 hours after excision, the percentage of mitotic figures was reduced to near 0 by 8 hours. In roots treated with chlorsulfuron plus isoleucine and valine, no reduction in mitotic figures occurred. The complete reversal of chlorsulfuron-inhibited mitotic entry by isoleucine and valine implicates these amino acids, in some manner, with the control of cell cycles progression.

Journal Article↗
PubMed1983

Isoleucyl-tRNA synthetase from Baker's yeast. Catalytic mechanism, 2',3'-specificity and fidelity in aminoacylation of tRNAIle with isoleucine and valine investigated with initial-rate kinetics using analogs of tRNA, ATP and amino acids.

The aminoacylation of three modified tRNAIle species with isoleucine and with valine by isoleucyl-tRNA synthetase has been investigated by initial rate kinetics. For aminoacylation of tRNAIle-C-C-3'dA with isoleucine, a bi-bi uni-uni ping-pong mechanism has been found by bisubstrate kinetics and inhibition by products and by 3'dATP; for aminoacylation with valine a bi-uni uni-bi ping-pong mechanism. For isoleucylation of tRNAIle-C-C-A(3'NH2) bisubstrate kinetics, inhibition by products and by isoleucinol show a random uni-bi uni-uni-uni ping-pong mechanism; for valylation of this tRNA a bi-bi uni-uni ping-pong mechanism is observed by bisubstrate kinetics and product inhibition. tRNAIle-C-C-2'dA was aminoacylated under modified conditions with isoleucine in a bi-bi uni-uni ping-pong mechanism with a rapid equilibrium segment as observed by bisubstrate kinetics, inhibition by AMP, by P[NH]P as product analog and by isoleucinol. Aminoacylation with valine is achieved in a rapid-equilibrium sequential random AB, ordered C mechanism indicated by bisubstrate kinetics and inhibition by 3'dATP and valinol. All six reactions exhibit orders of substrate addition and product release which are different from those observed in aminoacylation of the natural tRNAIle-C-C-A. The Km values of the three substrates and the kcat values of the six reactions are given. For aminoacylation at the terminal 2'OH group of the tRNA differences of 13.38 and 13.17 kJ in binding energies between valine and isoleucine have been calculated which result in discrimination factors of 181 and 167. For aminoacylation at the terminal 3'-OH group a difference of only 4.43 kJ and a low discrimination factor of only 6 is observed. Thus maximal discrimination between the cognate and the noncognate amino acid is only achieved in aminoacylation at the 2'-OH group and conclusions drawn from experiments with modified tRNAs concerning 2',3'-specificity have led to correct results in spite of different catalytic cycles in aminoacylation of the natural and the modified tRNAs. The stability of Ile-tRNAIle-C-C-2'dA and Val-tRNAIle-C-C-2'dA, the lesser stability of Val-tRNAVal-C-C-2'dA and the instability of Thr-tRNAVal-C-C-2'dA are consistent with postulations for a 'pre-transfer' proofreading step for isoleucyl-tRNA synthetase and a 'post-transfer' hydrolytic editing step for valyl-tRNA synthetase at the terminal 3'OH group of the tRNA.

Amino Acyl-tRNA Synthetases↗
PubMed1996

15N conservation in the metabolic conversion of isoleucine to alloisoleucine in the rat.

15N,13C6-L-Isoleucine was given by stomach tube to a pair of rats and the urine excreted over the following 6 h period was collected. The urinary amino acid fraction showed that the majority of the L-alloisoleucine produced from the labeled isoleucine was formed with the 15N label intact. This fails to support the commonly held supposition that L-isoleucine and L-alloisoleucine interconversion occurs through the reversible enolization of the 2-keto-3-methylvaleric acids formed by their transamination. In contrast to 15N label conservation in L-alloisoleucine, the majority of the 15N in the administered L-isoleucine underwent exchange with 14N.

Acetamides↗
PubMed1980

Mitochondrial protein synthesis in Chinese hamster cells (line CHO) synchronized by isoleucine deprivation.

Mitochondrial protein synthesis was measured in line CHO cells after phases of the cell cycle were synchronized by isoleucine deprivation or mitotic selection. Maximum incorporation of [3H] leucine into mitochondrial polypeptides occurred within 2 hours after isoleucine was added to initiate G1 traverse. In cells synchronized in G1 by mitotic selection, the rate of mitochondrial protein synthesis was fairly constant throughout the cell cycle. SDS-polyacrylamide gel electrophoretic profiles of labeled mitochondrial polypeptides were similar in cells synchronized by either isoleucine deprivation or mitotic selection. Obvious changes in the distribution of polypeptides were not detected during various phases of the cell cycle. The increased rate of incorporation of [3H] leucine into mitochondrial polypeptides after reversal of G1-arrest may indicate that mitochondrial protein synthesis and possibly mitochondrial biogenesis are synchronized in CHO cells deprived of isoleucine.

Animals↗
PubMed1988

Regulation of isoleucine-valine biosynthesis in Saccharomyces cerevisiae.

The threonine deaminase gene (ILV1) of Saccharomyces cerevisiae has been designated "multifunctional" since Bollon (1974) indicated its involvement both in the catalysis of the first step in isoleucine biosynthesis and in the regulation of the isoleucine-valine pathway. Its role in regulation is characterized by a decrease in the activity of the five isoleucine-valine enzymes when cells are grown in the presence of the three branched-chain amino acids, isoleucine, valine and leucine (multivalent repression). We have demonstrated that the regulation of AHA reductoisomerase (encoded by ILV5) and branched-chain amino acid transaminase is unaffected by the deletion of ILV1, subsequently revealing that the two enzymes can be regulated in the absence of threonine deaminase. Both threonine deaminase activity and ILV1 mRNA levels increase in mutants (gcd2 and gcd3) having constitutively depressed levels of enzymes under the general control of amino acid biosynthesis, as well as in response to starvation for tryptophan and branched-chain amino acid imbalance. Thus, the ILV1 gene is under general amino acid control, as is the case for both the ILV5 and the transaminase gene. Multivalent repression of reductoisomerase and transaminase can be observed in mutants defective in general control (gcn and gcd), whereas this is not the case for threonine deaminase. Our analysis suggests that repression effected by general control is not complete in minimal medium. Amino acid dependent regulation of threonine deaminase is only through general control, while the branched-chain amino acid repression of AHA reducto isomerase and the transaminase is caused both by general control and an amino acid-specific regulation.

Enzyme Repression↗
PubMed1997

[Plasma amino acid concentrations and isoleucine-phenylalanine quotient in patients with acute myocardial infarct during amino acid infusion].

AIM: The influence of substitution with two different amino acid solutions on changes in plasma amino acids were studied in patients with acute myocardial infarction. PATIENTS AND METHODS: Thirty consecutive patients admitted to an intensive care unit were included in this open, nonrandomized study. The isoleucine-phenylalanine-concentration ratio was calculated. Patients of the treatment groups received 10 ml/kg BW/24 h of 10% amino acid solutions intravenously (1 g/kg BW/24 h). Patients of group 1 received Intrafusin 10%, patients of group 2 Aminosteril 10%. Ten patients (group 3) were infused with 10 ml/kg BW/24 h isotonic electrolyte solution (Jonosteril and served as a control group. All infusions were performed over a 96 hour period. RESULTS: All infusion of amino acid solutions increased the plasma concentrations of most amino acids without a significant impact on the pattern of amino acids over time. Significant increases in plasma concentrations together with a significant variation over time were observed for glycine, isoleucine, proline, alpha-amino-butyric-acid and glutamine. A significant difference in relation to the type of amino acid solution was observed for isoleucine and proline (rapid increase and higher concentrations with Aminosteril), and glutamine (rapid increase and higher levels with Intrafusin). CONCLUSION: The isoleucine-phenylalanine-ratio increased from initially decreased values between 0.9 and 1.0 during amino acid infusion and reached the level of 1.25 found in healthy persons in patients with Intrafusin infusions.

Aged↗
PubMed1987

Specificity of the attenuation response of the threonine operon of Escherichia coli is determined by the threonine and isoleucine codons in the leader transcript.

Expression of the threonine (thr) operon enzymes of Escherichia coli is regulated by an attenuation mechanism. The regulatory portion of the operon contains a region coding for a leader peptide that contains consecutive threonine and isoleucine codons. It is thought that translation of the leader peptide controls the frequency of transcription termination at the attenuator site. Using oligonucleotide-directed site-specific mutagenesis we have altered the putative control codons of the leader peptide coding region. In two of the mutants the threonine and isoleucine codons were changed to produce peptides containing histidine and tyrosine codons. Both mutants showed loss of regulation by threonine and isoleucine. A hisT mutation, which leads to an undermodification of tRNA(His), increased thr operon expression in the mutants threefold but did not affect expression of the wild-type thr operon. Two other mutants were constructed that contained two histidine codons early in the leader peptide. Expression in both of these mutants was unaltered by the presence of the hisT allele or by the addition of threonine and isoleucine to the growth medium. In addition, a wild-type strain containing a temperature-sensitive threonyl-tRNA synthetase mutation showed increased thr operon expression at the non-permissive temperature, whereas none of the mutants showed any change. Taken together these data indicate that the specificity of the attenuation response is effected by specific control codons within the thr leader peptide coding region. We have also directly demonstrated thr leader peptide synthesis in vitro using a plasmid encoding the wild-type thr leader region to direct the synthesis of a peptide of the appropriate molecular weight when labeled with [3H]threonine but not with [3H]histidine or [3H]tyrosine. Conversely, when extracts were incubated with templates containing the mutated DNAs, peptides were labeled that showed patterns consistent with the expected amino acid compositions. These data indicate that the thr leader RNA is translated into the predicted leader peptide.

Codon↗
PubMed1977

The exclusion of L-isoleucine or of L-leucine from the brain of the rat, caused by raised levels of L-valine in the circulation, and the manner in which this exclusion can be partially overcome.

The amino acids L-isoleucine, L-leucine and L-valine appear to compete for a shared transport carrier for entry into the brain of the living rat, since high concentrations of L-valine in the plasma reduced the influx both of L-isoleucine and of L-leucine into the brain to 10-15% of the normal. The exclusion of L-isoleucine or of L-leucine from the brain by a raised level of L-valine in the circulation can be partially overcome by simultaneously raising the concentration of L-isoleucine or of L-leucine in the circulation. These results indicate the important role played by a saturable shared carrier-mediated transport system in ensuring that an adequate supply of these amino acids reaches the brain from the circulation during life. The bearing of our findings on two inborn errors of amino acid metabolism, maple-syrup-urine disease and hypervalinaemia, is discussed.

Animals↗
PubMed1989

Transamination and oxidative decarboxylation of L-isoleucine, L-alloisoleucine and related 2-oxo acids in perfused rat hind limb muscle.

Metabolism of L-isoleucine, L-alloisoleucine and corresponding 2-oxo acids in rat hind limb muscle was comparatively studied under steady-state perfusion conditions. At 0.5 mM L-[1-14C]isoleucine, apparent transamination and 2-oxo acid decarboxylation rates amounted to about 17 and 4 nmol/min per g of muscle, respectively. With L-allo[1-14C]isoleucine, the corresponding rates were about 5- and 10-fold lower, respectively. After addition of dichloroacetate (1-5 mM), the portion of (S)- and (R)-methyl-2-oxopentanoate undergoing further oxidative decarboxylation within the tissue was similarly increased by over 40%. In perfusions with 0.5 mM (R,S)-3-methyl-2-oxopentanoate and tracer doses of 1-14C-labeled (S)- or (R)-enantiomer, the 14CO2 production was comparable (about 0.5 nmol/min per g of muscle). Dichloroacetate caused a several-fold increase in 14CO2 release from either enantiomer, apparent 2-oxo acid transamination rates remaining unaffected. Indications for a racemization of 2-oxo acid were not obtained in the experiments. The results are discussed with respect to the appearance/disappearance of L-alloisoleucine in vivo and to the fact that (R)-3-methyl-2-oxopentanoate, but not L-alloisoleucine, can support growth of rats on a diet deficient in L-isoleucine.

Alanine↗
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↗