Threonine O-phosphate

Phospho-L-threonine (L-threonine-O-phosphate) [1114-81-4] M 199.1, m 194 (dec), [a]p -7.37 (c 2.8, H2O) (pK as above). Dissolve in the minimum volume of H2O, add charcoal, stir for a few min, filter and apply onto a Dowex 50W (H" " form) then elute with 2N HCI. Evaporate the eluates under reduced pressure whereby the desired fraction produced crystals of the phosphate which can be recrystd from H2O-MeOH mixtures and the crystals are then dried in vacuo over P2O5 at 80 . [de Verdier Acta Chem Scand 7 196 7955.]... 

Figure 4 Coenzymes of methanogenesis. F-430, coenzyme M (2-thioethanesulfonate), and coenzyme B (7-thioheptanoyl-threonine-O-phosphate [sometimes abbreviated HS-HTP]). Methyl-reducing factor is a structure proposed on the basis of NMR and mass spectrometry, in which the phosphate group of CoB is linked by a carboxylic-phosphoric anhydride to a UDP disaccharide, uridine 5 -(2-acetamido-2-deoxymannopyranuronosyl)-2-acetamido-2-deoxy-glucopyranosyl-diphosphate [171]. The CoB moiety without it appears to be functionally active in the enzyme reaction.

Alkaline hydrolysis with barium, sodium, or lithium hydroxides (0.2-4 M) at 110°C for 18-70 h126-291 requires special reaction vessels and handling. Reaction mixtures are neutralized after hydrolysis and barium ions have to be removed by precipitation as their carbonate or sulfate salts prior to analysis which leads to loss of hydrolysate. Correspondingly, peptide contents are difficult to perform by this procedure. Preferred conditions for alkaline hydrolysis are 4M LiOH at 145 °C for 4-8 h where >95% of tryptophan is recovered 291 An additional inconvenience of the alkaline hydrolysis procedure is the dilution effect in the neutralization step and thus the difficult application to the analyzer if micro-scale analysis is to be performed. The main advantage is the good recovery of tryptophan and of acid-labile amino acid derivatives such as tyrosine-0-sulfate1261 (Section 6.6) as well as partial recovery of phosphoamino acids, particularly of threonine- and tyrosine-O-phosphate (Section 6.5). 

Cysteinylheme S-Cysteinyl phycocyanobilin Cysteine-S-phosphate Threonine O -Phosphothreonine Glycosylation... 

Finally, because this modification occurs on serine and threonine residues, it can also compete directly with an O-phosphory lation event at an identical or nearby site to provide an additional level of regulation on a specific protein. To date, all described O-GlcNAc-modified proteins have been found to be phospho-proteins (28, 29, 30). Such competition between O-GlcNAc and O-phosphate binding occurs with many examples listed above as well as with others. 

The pyridoxal biosynthetic pathway is outlined in Fig. 37. Oxidation of 196 followed by transamination gives 4-hydroxy-L-threonine-4-phosphate 199 [171]. Condensation with l-deoxy-o-xylulose (see also ubiquinone and thiamin sections) and a final oxidation gives the cofactor [172-175]. 

In transit through the ER and Golgi, the proteins acquire oligosaccharide side chains attached commonly at serine or threonine residues (O-linked) or at asparagine residues (N-linked). N-linked glycosylation requires participation of a special lipid called dolichol phosphate. 

Amino acid side chains at the positions X, Y, Z, -Y,-X, and —Z (illustrated in Fig. 29) of EF hands and other calcium-binding regions are listed. D, Aspartic acid E, glutamic acid N, asparagine S, serine T, threonine Ox, main-chain carbonyl Wa, water Ph, phosphate O -, a number of intervening amino acids. 

Vanadyl and copper(n) ions catalyse the /J-elimination reaction of O-phospho-threonine in the presence of pyridoxal.429 Equilibrium spectroscopic studies of the threonine-metal ion-pyridoxal system have identified a metal-ion complex of the amino-acid-pyridoxal Schiff base. The catalytic effect of the metal is ascribed to its electron-with drawing effecCIt was suggested that the specific catalytic effect of Cu2 + and V02+ arises from their reluctance to co-ordinate the phosphate in an axial position. Other metal ions such as nickel can also form the Schiff base complex but probably stabilize the phosphothreonine system by chelate formation. 

In enzymatic reactions, the transfer proceeds via phosphorylation of the OH function of the serine residue however, threonine and tyrosine can be also involved. Hence, much attention has been paid to the fundamental study of the compounds shown in Scheme 2.36 The attractiveness of these models is due to the fact that X-ray structures both for enantiomeric and racemic forms are known (with exception of O-phospho-L-tyrosine). With the local geometry of phosphate groups and hydrogen bonding pattern taken from X-ray studies, it is possible to test the correctness of NMR analysis, the accuracy of measured structural constraints and the applicability of theoretical methods (ab initio, density functional... 

The CHF and CF2 groups are superior to CH2 as isosteres of oxygen and this has led to extensive interest in their chemistry. The a-difluorophosphonate analogues of the phosphates of L-serine (219), L-threonine (220), and L-allothreonine (221) have been prepared by highly enantioselective reactions of difluoromethylpho-sphonate carbanion with chiral esters. Lipase PS catalysed acetylation of prochiral 1,3-propandiol alkylphosphonates 222 is reported to be highly enantioselective and the resulting monoacetate enantiomers 223 have been used to synthesise a series of (o-phosphono-a-amino acids, 224 and 225.Other routes to 225, one of... 

Figure 9. HPLC of CBZ-L-threoninamlde using a Waters Radial Pak C] 8 Cartridge (10 x 8 mm l.d.). Mobile phase 82% O.IH phosphate buffer (pH 3,0) - 18% methanol. Flow rate 2 mL/mln. Detection UV 204 nm. Peaks (1) = I.-threonine, (2) benzyl alcohol, (3) = CBZ-L-threonlne, (4) = benzyl carbamate, (5) CBZ-I.-threonlna-mlde.

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