Valine isolation

Zhang Q, Spiers DE, Rottinghaus GE, Gamer GB. Thermoregulatory effects of ergo valine isolated from endophyte-infected tall fescue seed on rats. J Agric Food Chem 42 954-958, 1994. 

L-Valine isolated from extracts of pancreas gland by E.v. Gorup-Besanez, as racemate from baryta-hydrolyzed protein by P. Schiitzenberger, 1879, as L-valine from HCl-hydrolyzate of casein in 1901 by E. Fischer, who also established its structure as a-amino-isovaleric acid and named it valine in 1906. 

Stepanian, S. G., Reva, I. D., Radchenko, E. D., Adamowicz, 1999, Combined Matrix-Isolation Infrared and Theoretical DFT and Ab Initio Study of the Nonionized Valine Conformers , J. Phys. Chem. A, 103, 4404. 

The second and most important finding of this sequencing project was that the difference of 14 Da between the two proteins was not because of a methy-lation of the protein isolated from chicken but because of a substitution of valine for leucine. The MS/MS analysis of the tryptic pieces in which the substitution occurred is shown in Figure 10.11. Had this been a bottom-up... 

Christensen16 isolated the dipeptide valylvaline from completely hydrolyzed gramicidin. This worker later showed that he had isolated a racemic mixture of D(-)-valyl-D(-)-valine and L(+)-valyl-L(4)-valine rather than dipeptides containing one d and one L-residue.17... 

Still using heterogeneous gramicidin, Synge24 isolated the D-leucylglycine, L-alanyl-D-valine and L-alanyl-D-leucine from partial hydrolysates of gramicidin. He also had less conclusive evidence for the tripeptides alanyl-valylleucine or alanylleucylvaline. 

The main disadvantages of Evans auxiliaries 22 and 23 are that they are expensive to purchase and inconvenient to prepare, as the preparation involves the reduction of (5 )-valine 24 to water-soluble (b )-valinol, which cannot be readily extracted to the organic phase. The isolation of this water-soluble vali-nol is difficult and requires a high vacuum distillation, which is not always practical, especially on an industrial scale. Therefore, an efficient synthesis of Evans chiral auxiliary 25 has been developed, as depicted in Scheme 2-1930 ... 

By means of a procedure described above, Hanson and Fittkau (HI) isolated seventeen different peptides from normal urine. One of them, not belonging to the main peptide fraction, consisted of glutamic acid, and phenylalanine with alanine as the third not definitely established component. The remaining peptides contained five to ten different amino acid residues and some unidentified ninhydrin-positive constituents. Four amino acids, i.e., glutamic acid, aspartic acid, glycine, and alanine, were found in the majority of the peptides analyzed. Twelve peptides contained lysine and eight valine. Less frequently encountered were serine, threonine, tyrosine, leucine, phenylalanine, proline, hydroxyproline, and a-aminobutyric acid (found only in two cases). The amino acid composi-... 

The action of the valine derivatives 87 on the diene 86 under EtAlCU catalysis resulted in a mixture of cycloadducts 88, which on hydrolysis with aqueous methanolic sodium carbonate furnished a mixture of the dihydro-2-pyridones 89 and 90 and the esters 91 and 92. In the case of imines derived from aliphatic aldehydes, e.g. 87 (R = Pr), all four types of product were isolated, whereas imines from aromatic aldehydes, 87 (R = Ph, 3-CIC6H4 etc.), gave only the esters 91 and 92 (equation 55). All products were formed in yields of 64-84% and in high de49. 

Roe CR, Cederbaum SD, Roe DS, Mardach R, Galindo A, Sweetman L. Isolated isobutyryl-CoA dehydrogenase deficiency an unrecognized defect in human valine metabohsm. Mol Genet Metab. 1998 Dec 65(4) 264-71. PubMed citation... 

Isolated isobutyryl-CoA dehydrogenase deficiency an unrecognized defect in human valine metabolism. 

Isolation of individual amino acids started about 1820 by 1904 all of the naturally occurring amino acids in proteins had been isolated except methionine (Mueller, 1922) and threonine (Rose, 1937). One of the earliest methods for the separation of amino acids was through the differential volatility of their methyl or ethyl esters (Emil Fischer, 1901). This approach led to the discovery of valine, proline, and hydroxyproline. [In the 1970s Fischer s method was modified for microanalysis of proteins, separating the amino acid esters by gas phase chromatography. Separation is now usually performed by hplc (high pressure liquid chromatography).]... 

Capsaicinoids are synthesized by the condensation of vanillylamine with a short chain branched fatty acyl CoA. A schematic of this pathway is presented in Fig. 8.4. Evidence to support this pathway includes radiotracer studies, determination of enzyme activities, and the abundance of intermediates as a function of fruit development [51, 52, 57-63], Differential expression approaches have been used to isolate cDNA forms of biosynthetic genes [64-66], As this approach worked to corroborate several steps on the pathway, Mazourek et al. [67] used Arabidopsis sequences to design primers to clone the missing steps from a cDNA library. They have expanded the schema to include the biosynthesis of the key precursors phenylalanine and leucine, valine and isoleucine. Prior to this study it was not clear how the vanillin was produced, and thus the identification of candidate transcripts on the lignin pathway for the conversion of coumarate to feruloyl-CoA and the subsequent conversion to vanillin provide key tools to further test this proposed pathway. 

The enzymes that are involved in the conversion of tyrosine to the aldoximes, 25 and 26 02.105 pj tryptophan , phenylalanine , valine and isoleucine " to the corresponding aldoximes are the multifunction cytochrome P450. CYP79A1, that hydroxylates tyrosine, was isolated from Sorghum bichlor and subsequently cloned". These oximes are the building blocks of plant glucosinolates, 15, and glycosides, 16. 

Valine.—This amino acid is contained mixed with leucine in the fractions of the esters which boil between 6o° and 90° C. Its isolation and separation from leucine is of extreme difficulty, since these compounds, as well as their copper salts into which they are converted by boiling with freshly precipitated cupric oxide, tend to form mixed crystals. Its isolation was only effected by these means in certain cases, and its amount is really much more than the figures represent from its yield. It is best characterised by conversion into its phenylhy-dantoine derivative by treatment with phenyl isocyanate in alkaline solution. The phenylureido acid is first formed, and this loses a molecule of water, as shown by Mouneyrat, and is changed into its anhydride or phenylhydantoine by treatment with hydrochloric acid. The following reactions occur —... 

Leucine.—The greater part of the leucine is contained in the ester fractions, which boil between 70° and 90° C. It generally occurs in considerable amounts in the protein, and is obtained by crystallisation from water, in which it is less soluble than the other amino acids which may be present. It is seldom present in its pure, optically active form, as this is easily racemised, and the various crops of crystals most probably also contain isoleucine. It is more easily isolated by completely racemis-ing the mixture of amino acids contained in this fraction by heating in an autoclave with baryta to 160-180° C., and then, after removal of the baryta, separating it by crystallisation. The difficulty of separating it from the other amino acids, especially valine and isoleucine, makes an exact quantitative estimation almost impossible. The values which have been found are therefore minimal ones, and they will also include in many cases the yield of isoleucine. 

Hi. Lysine. Gamma radiolysis of aerated aqueous solution of lysine (94) has been shown, as inferred from iodometric measurements, to give rise to hydroperoxides in a similar yield to that observed for valine and leucine. However, attempts to isolate by HPLC the peroxidic derivatives using the post-column derivatization chemiluminescence detection approach were unsuccessful. This was assumed to be due to the instability of the lysine hydroperoxides under the conditions of HPLC analysis. Indirect evidence for the OH-mediated formation of hydroperoxides was provided by the isolation of four hydroxylated derivatives of lysine as 9-fluoromethyl chloroformate (FMOC) derivatives . Interestingly, NaBILj reduction of the irradiated lysine solutions before FMOC derivatization is accompanied by a notable increase in the yields of hydroxylysine isomers. Among the latter oxidized compounds, 3-hydroxy lysine was characterized by extensive H NMR and ESI-MS measurements whereas one diastereomer of 4-hydroxylysine and the two isomeric forms of 5-hydroxylysine were identified by comparison of their HPLC features as FMOC derivatives with those of authentic samples prepared by chemical synthesis. A reasonable mechanism for the formation of the four different hydroxylysines and, therefore, of related hydroperoxides 98-100, involves initial OH-mediated hydrogen abstraction followed by O2 addition to the carbon-centered radicals 95-97 thus formed and subsequent reduction of the resulting peroxyl radicals (equation 55). 

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