Amino acid orthophosphates

Figure 6.4 Experimental curves for equilibrium gel filtration, (a) The 1-mL tuberculin syringe was incubated in 109-pAf[14C]valine (O) or 109-/zM[14C]valine and 4-mM ATP ( ). Then 100 fjL of a solution of 26-fiM valyl-tRNA synthetase was added to the same solution. Stoichiometries of 0.8 and 1.1, respectively, were found for the binding of the amino acid. Note the return to baseline between the peak and the trough— the mark of a good equilibrium gel filtration experiment, (b) An artifact-induced double peak obtained from the binding of [y-32P]ATP and valine to the enzyme. Some of the labeled ATP hydrolyzed to [32P]orthophosphate, which traveled down the column faster than the fy-32P]ATP did.

However, most nucleophiles attack 5-oxazolones at the carbonyl group and the products are derivatives of a-amino acids formed by acyl-oxygen fission. Thus the action of alcohols, thiols, ammonia and amines leads, respectively, to esters, thioesters and amides orthophosphate anion gives acyl phosphates (Scheme 18). The use of a-amino acids in this reaction results in the establishment of a peptide link. Cysteine is acylated at the nitrogen atom in preference to the sulfur atom. Enzymes, e.g. a-chymotrypsin and papain, also readily combine with both saturated and unsaturated azlactones. A useful reagent for the introduction of an a-methylalanine residue is compound (202). Both the trifluoroacetamido and ester groups in the product are hydrolyzed by alkali to give a dipeptide. The alkaline hydrolyzate may be converted into the benzyloxycarbonyl derivative, which forms a new oxazolone on dehydration. Reaction with an ester of an amino acid then yields a protected tripeptide (equation 45). 

Pyrophosphate is then hydrolyzed to orthophosphate, and so the equivalents of two compounds having high phosphoryl transfer potential are consumed in the activation of acetate. We will return to this type of activation reaction in fatty acid degradation (Section 22.2.2). where it is used to form fatty acyl CoA, and in protein synthesis, where it is used to link amino acids to transfer RNAs (Section 29.2.1). 

The aromatic amino acid tyrosine has proved successful as an eluent for the simultaneous analysis of all halide anions, which also causes a reduction in the iodide retention at alkaline pH, while still allowing for the separation of bromide and nitrate in contrast to p-cyanophenol containing eluents. In the respective chromatogram obtained with tyrosine as the eluent, a reversed retention is observed for orthophosphate and sulfate. This is caused by the comparatively high pH value of the mobile phase. The... 

Further studies on this system with carbobenzoxyglycyl-L-phenylalanine (CGP) and carbobenzoxyglycyl-L-leucine (CGL) as the substrates led to the conclusion that orthophosphate, pyrophosphate, oxalate, citrate, and cyanide did not affect the initial rate of hydrolysis significantly (Neurath and de Maria, 1950). In the presence of these anions, competitive inhibition by the liberated amino acid was found to occur. These authors concluded that the anions had no effect on the enzymatic activation process and that the hypothesis that carboxypeptidase is a magnesium enzyme was devoid of experimental evidence. 

UV-active anions and cations, transition metals after reaction with 4-(2-pirydyloazo) rezordnol (PAR), aluminum after reaction with tiron, lanthanides after reaction with arsenazo I, polyvalent anions after reaction with iron(III), silicate and orthophosphate after reaction with molybdate Ammonium, amino acids, and primary amines after reaction with 0-phenylamine (OPA) Anions and cations at higher concentrations... 

Preparative scale reduction of oximes at a mercury or lead cathode in acid solution has been used in the conversion of the carbonyl function to amine. Originally, 30-50% sulphuric acid was used as solvent [195] but ethanol with dilute hydrochloric acid is usually satisfactory. Aliphatic and aromatic oximes give amines in 64-86% yields [196]. Aromatic ketoximes are also reducible in alkaline solution and acetophenone oxime has been converted to 1-phenylethylamine in a tri-potassium orthophosphate solution [197], The reduction of oximes in acid solution is tolerant of many other substituents as indicated by a number of examples [198, 199, 200. Phenylglyoxa monoxime in acid solution is however reduced at both the carbonyl and the oxime centres by sodium amalgam to yield 2-amino-1-phenylethanol [201]... 

The calcium salt of 2-amino-2-deoxy-D-glucosyl phosphate has been synthesized37 by the interaction of 2-acetamido-3,4,6-tri-0-acetyI-2-deoxy-a-D-glucosyl chloride with silver orthophosphate, with subsequent partial saponification. On the basis of optical rotation, the derivative has been assigned to the a-n series. 2-Amino-2-deoxy-D-glucosyl phosphate is much less stable than the 6-phosphate toward acidic hydrolysis, but it is markedly more... 

Orthophosphate forms a complex with the molybdate ion in the presence of a reducing agent such as hydrazine sulfate, amino-naphthol-sulfo-nic acid, tin(II) chloride, or ascorbic acid, which is commonly called heteropoly blue and has a molecular formula H3P04(Mo03)]2 (2). There are two wavelengths that can be used one between 625 and 650 nm and a more sensitive one at 830 nm. The Spectronic 21 DUV is capable of measuring up to 1000 nm and the Spectronic 20 can go only up to 600 nm with the standard phototube. An infrared phototube is necessary to widen the wavelength of this instrument. 

Diammonium hydrogen orthophosphate Diammonium hydrogen phosphate. See Ammonium phosphate, dibasic Diammonium lauramido-MEA sulfosuccinate Synonyms Butanedioic acid, sulfo-, 1- [2- [(1-oxododecyl) amino] ethyl] ester, diammonium salt Sulfobutanedioic acid, 1-ester with N-(2-hydroxyethyl) dodecanamide, diammonium salt... 

Acacia Acetylated lard glyceride Acrylic acid/acrylamide copolymer Adipic acid Allyltrimethoxysilane Allyltrimethyl silane Aluminum orthophosphate N-(2-Aminoethyl)-3-aminopropyl methyidimethoxy silane 3-Aminopropylmethyldiethoxysilane Aminopropyltrimethoxysilane Ammonium hydroxide Ammonium molybdate (VI) Ammonium ricinoleate Amyltrichlorosilane Arachidyl alcohol Barium petroleum sulfonate Bis (dimethylamino) dimethylsilane 3-[Bis (2-hydroxyethyl) amino] propyltriethoxysilane Bis-(N-methylbenzamide) ethoxymethyl silane Bismuth... 

---