Tyrosine production

We know that this is the mechanism because we can make the green H a deuterium atom. We then find that deuterium is present in the tyrosine product ortho to the phenolic hydroxyl group. When the migration occurs, the deuterium atom must go as there is no alternative, but in the next step there is a choice and H loss will be preferred to D loss because of the kinetic isotope effect (Chapter 19). Most of the D remains in the product. 

Treatment of proteins with nitrous acid can lead to deamination of the lysyl residues as well as of the NH2-terminal residues. Kurosky and Hoffmann (1972) have identified three products of lysine deamination which elute from the 60 cm column of a Beckman 120C Analyzer at (1) the position of glutamic acid, (2) 7 min before glycine and (3) 10 min before tyrosine. Products (2) and (3), which are the major products formed, are believed to be s-hydroxynorleucine and its lactone respectively. The most accurate method for analyzing for lysine deamination is to measure the loss of lysine rather than to measure the three derivatives. 

Aerobic additions of nitric oxide, ONOO , or both all resulted in formation of only 4-nitrosophenol, whereas both 2- and 4-nitrophenol were formed from ONOO". The lack of 2-nitrosophenol production has particular relevance to the tyrosine products, which could be produced and measured either in vivo or in vitro. The side chain of tyrosine exists at the position that corresponds to the 4-position of phenol. Thus, 4- or p-nitrosotyrosine cannot exist. The o-position to the hydroxyl of tyrosine is equivalent to the 2-position of phenol. 

Chavez-Bejar, M.l. et al (2008) Metabolic engineering of Escherichia coli for L-tyrosine production by expression of genes coding for the chorismate mutase domain of the native chorismate mutase-prephenate dehydratase and a cyclohexadienyl dehydrogenase from Zymomonas... 

Santos, C.N.S., Xiao, W., and Stephanopoulos, G. (2012) Rational, combinatorial and genomic approaches for engineering L-tyrosine production in Escherichia coli. Proc. Natl Acad. 

Patnaik, R., Zolandz, R.R., Green, D.A., and Kraynie, D.F. (2008) L-Tyrosine production by recombinant Escherichia coli fermentation optimization and recovery. Biotechnol Bioeng., 99, 741-752. 

L-Tyrosine Production from Simple Sources of Carbon. 14... 

Hagino H, Nakayama K (1973) L-Tyrosine production by analog-resistant mutants derived from a phenylalanine auxotroph of Corynebacterium glutamicum. Agric Biol Chem 39 2013-2023... 

Liitke-Eversloh T, Stephanopoulos G (2007) L-tyrosine production by deregulated strains of Escherichia coli. Appl Microbiol Biotechnol 75 103—110... 

LynF, an enzyme from the TruF family, 0-prenylates tyrosines in proteins and subsequent Claisen rearrangements give C-prenylated tyrosine products. The reactions in tyrosines and model phenolic systems have been explored with computational methods. Studies of the orf/to-C-prenylation and Claisen rearrangement of tyrosine and the Claisen rearrangement of a,a-dimethylallyl (prenyl) coumaryl ether establish the energetics of in the gas phase and in aqueous solution (Scheme 29). ... 

The mechanism of iron dependent hydroxylation by RLPAH was compared with that of the metal-independent one by CVPAH to clarify the role of iron in the mechanism of RLPAH [122]. A kinetic isotope effect, / d, on hydroxylation of [4- H]-phenylalanine as a substrate is unity for CVPAH, which is in agreement with values for RLPAH [123]. An NIH shift was observed with the [4- H]-phenylalanine upon hydroxylation by CVPAH as by RLPAH [124-126]. The extent of deuterium retention at the 3-position of the tyrosine product was identical within experimental error for both CVPAH and... 

C. Excreted in the urine in the rare hereditary disease alkaptonuria. Homogentisic acid is easily oxidized in the air to dark-coloured polymeric products, so that urine from patients with alkaptonuria turns gradually black. It is formed from tyrosine and is an intermediate in tyrosine breakdown in the body. Alkaptonuria is due to the absence of the liver enzyme which cleaves the aromatic ring. 

The mode of action is by inhibiting 5-enolpymvyl-shikimate-3-phosphate synthase. Roundup shuts down the production of the aromatic amino acids phenylalanine, tyrosine, and tryptophane (30). Whereas all these amino acids are essential to the survival of the plant, tryptophane is especially important because it is the progenitor for indole-3-acetic acid, or auxin, which plays an important role in growth and development, and controls cell extension and organogenesis. 

Amino acid-derived hormones include the catecholamines, epinephrine and norepinephrine (qv), and the thyroid hormones, thyroxine and triiodothyronine (see Thyroid AND ANTITHYROID PREPARATIONS). Catecholamines are synthesized from the amino acid tyrosine by a series of enzymatic reactions that include hydroxylations, decarboxylations, and methylations. Thyroid hormones also are derived from tyrosine iodination of the tyrosine residues on a large protein backbone results in the production of active hormone. 

One Anson unit is the amount of enzyme that, under standard conditions, digests hemoglobin at an initial rate, Hberating per minute an amount of TCA-soluble product which produces the same color with phenol reagent as one milliequivalent of tyrosine (91). 

Catecholamine biosynthesis begins with the uptake of the amino acid tyrosine into the sympathetic neuronal cytoplasm, and conversion to DOPA by tyrosine hydroxylase. This enzyme is highly localized to the adrenal medulla, sympathetic nerves, and central adrenergic and dopaminergic nerves. Tyrosine hydroxylase activity is subject to feedback inhibition by its products DOPA, NE, and DA, and is the rate-limiting step in catecholamine synthesis the enzyme can be blocked by the competitive inhibitor a-methyl-/)-tyrosine (31). 

Figure 4.16 A schematic view of the active site of tyrosyl-tRNA synthetase. Tyrosyl adenylate, the product of the first reaction catalyzed by the enzyme, is bound to two loop regions residues 38-47, which form the loop after p strand 2, and residues 190-193, which form the loop after P strand 5. The tyrosine and adenylate moieties are bound on opposite sides of the P sheet outside the catboxy ends of P strands 2 and 5.

This reaction was studied by use of tritium. The phenylalanine was labeled with tritium at the 4-position of the phenyl ring. When the product, tyrosine, was isolated, it retained much of the original radioactivity, even though the 4-position was now substituted by a... 

A method that has been the standard of choice for many years is the Lowry procedure. This method uses Cn ions along with Folin-Ciocalteau reagent, a combination of phosphomolybdic and phosphotnngstic acid complexes that react with Cn. Cn is generated from Cn by readily oxidizable protein components, such as cysteine or the phenols and indoles of tyrosine and tryptophan. Although the precise chemistry of the Lowry method remains uncertain, the Cn reaction with the Folin reagent gives intensely colored products measurable spectrophotometrically. 

A mixture was made of L-tyrosine (18.1 g, 0.1 mol) benzoyl chloride (7.0 g, 0.05 mol) and 200 ml anhydrous THF. After stirring at reflux for 2 hours, the mixture was cooled to room temperature, and the precipitate of tyrosine hydrochloride filtered off (11 g, 46 meq. Cr). The THF was evaporated and the residue extracted with CCI4 (3 X 100 ml at reflux, discarded) and then dissolved in ethyl acetate (200 ml) filtering off insolubles. The ethyl acetate solution was evaporated to yield 13.2 g solid product, MP 159°-162°C (93%). The tyrosine was recovered (8 g) by neutralization with aqueous alkali, from the hydrochloride. 

A solution was made of N-benzyl-L-tyrosine (5.7 g, 20 mmols) and N-methylmorphollne (2,04 g, 20 mmols) In 60 ml of THF, at -15°C, and to it was added ethyl chloroformate (2,08 g, 20 mmols), After 12 minutes, p-aminobenzoic acid (2.74 g, 20 mmols) dissolved in 25 ml of THF and 0.38 g of p-toluenesulfonic acid (2 mmols) were added, and the temperature allowed to rise to 5°C. After 2 hours and forty minutes, the mixture was poured into 1 liter of 0,1 N cold HCI, stirred one-half hour, filtered and dried, to give 8,7 g, MP 192°-223°C. The product was recrystallized from 90 ml methanol and 40 ml water, to give 6 g (74%) of product, N-benzoyl-L-tyrosyl-p-amlnobenzoic acid, MP 240°-242°C. 

Although some applications for preparative-scale separations have already been reported [132] and the first commercial systems are being developed [137, 138], examples in the field of the resolution of enantiomers are still rare. The first preparative chiral separation published was performed with a CSP derived from (S -N-(3,5-dinitrobenzoyl)tyrosine covalently bonded to y-mercaptopropyl silica gel [21]. A productivity of 510 mg/h with an enantiomeric excess higher than 95% was achieved for 6 (Fig. 1-3). 

Iborra and co-workers (Entry 8) examined the transesterification of N-acetyl-i-tyrosine ethyl ester in different ionic liquids and compared their stabilizing effect relative to that found with 1-propanol as solvent [36]. Despite the fact that the enzyme activity in the ionic liquids tested reached only 10 to 50 % of the value in 1-propanol, the increased stability resulted in higher final product concentrations. Fixed water contents were used in both studies. 

Production of phenylalanine starts after depletion of tyrosine at about 6 hours. This is logical since the micro-oiganism needs a certain amount of tyrosine, for example to synthesise key enzymes, but synthesis of L-phenylalanine is feedback regulated if tyrosine is present. 

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