Acetate phosphorylation

A familiar example of this type of metabolite adaptation is the thiol ester derivative of acetic acid, acetyl-coenzymeA (acetylCoA). AcetylCoA has a much larger negative free energy of hydrolysis than acetate, so metabolic transformations involving the acetate ion can occur with much lower concentrations of acetylCoA than of acetate. Phosphorylated metabolic intermediates likewise allow metabolites to have high chemical potentials and occur at relatively low concentrations in the cellular water. Use of such activated intermediates enables the cell to avoid high concentrations of metabolites that can tax solvent capacity and, perhaps more important, disrupt the cell through uncontrolled chemical reactions with inappropriate molecules. 

In keeping with its biogenetic origin m three molecules of acetic acid mevalonic acid has six carbon atoms The conversion of mevalonate to isopentenyl pyrophosphate involves loss of the extra carbon as carbon dioxide First the alcohol hydroxyl groups of mevalonate are converted to phosphate ester functions—they are enzymatically phosphorylated with introduction of a simple phosphate at the tertiary site and a pyrophosphate at the primary site Decarboxylation m concert with loss of the terti ary phosphate introduces a carbon-carbon double bond and gives isopentenyl pyrophos phate the fundamental building block for formation of isoprenoid natural products... 

Phosphorylated cottons are flame resistant ia the form of the free acid or the ammonium salt. Siace these fabrics have ion-exchange properties, conversion to the sodium salt takes place readily during laundering if basic tap water is used. However, flame resistance can be restored if the fabric is treated with either acetic acid [1563-80-8] or ammonium hydroxide [1336-21 -6] after washing. 

Fig. 2. Synthesis of uma2enil (18). The isonitrosoacetanihde is synthesized from 4-f1iioroani1ine. Cyclization using sulfuric acid is followed by oxidization using peracetic acid to the isatoic anhydride. Reaction of sarcosine in DMF and acetic acid leads to the benzodiazepine-2,5-dione. Deprotonation, phosphorylation, and subsequent reaction with diethyl malonate leads to the diester. After selective hydrolysis and decarboxylation the resulting monoester is nitrosated and catalyticaHy hydrogenated to the aminoester. Introduction of the final carbon atom is accompHshed by reaction of triethyl orthoformate to...

Finally, the importance of quinolinium salts to dye chemistry accounts for the long, productive history of their synthesis. The reaction of A/-methylformanihde with ketones, aldehydes, ketone enamines, or enol acetates in phosphoryl chloride leads to high yields of /V-methylquinolinium salts (60). 

As summarized in Figure 27.7, the mevalonate pathway begins with the conversion of acetate to acetyl CoA, followed by Claisen condensation to yield acetoacety) CoA. A second carbonyl condensation reaction with a third molecule of acetyl CoA, this one an aldol-like process, then yields the six-carbon compound 3-hydroxy-3-methylglutaryl CoA, which is reduced to give mevalonate. Phosphorylation, followed by loss of C02 and phosphate ion, completes the process. 

Fischer projections and, 977-978 glycosides of, 989-990 hemiacetals of, 984-986 osazones from, 1013 oxidation of, 992-994 phosphorylation of, 991 reaction with acetic anhydride, 988... 

Pyrido[2, l-6]quinazolinone (analogous to 204) and its 2,8-dinitro derivative were brominated by bromine in acetic acid, but the products are of unknown structure. Reaction with a mixture of phosphoryl chloride and... 

Phosphoryl chloride [10025-87-3], 4 Phthalamic acid, A V-diethyl-, methyl ester [2659344-2],63 Piperidine [110-894], 86, 118 acetate [4540-334], 118 Piperidine, 1 chloro- [2156-71-0], 118 Potassium cyanide [151-50-8], 20... 

For the hydrolysis of acetyl phosphate under the conditions prevailing in the body, AG = —41 kj-mol. If the phosphorylation of acetic acid (the reverse of the hydrolysis of acetyl phosphate) was driven by coupling to the hydrolysis of ATP at pH = 7, what is the minimum amount of ATP molecules (in moles) that would have to be hydrolyzed to form... 

Acetate kinase is phosphorylated by acetyl phosphate and it has been shown that the phosphoenzyme can synthesise ATP from ADP, and acetyl phosphate from acetate. The mode of decomposition of carbamyl phosphate in aqueous solution is pH dependent and can proceed with either the production of ammonia and carbon dioxide (equation 1), or cyanate (equation 2). No cyanate could be detected during the hydrolysis... 

The reaction of acetic anhydride with glycerol in the presence of phosphoryl trichloride as a catalyst was carried out the following way ... 

D-Xylulose 5-phosphate (ii-threo-2-pentulose 5-phosphate, XP) stands as an important metabolite of the pentose phosphate pathway, which plays a key fimction in the cell and provides intermediates for biosynthetic pathways. The starting compound of the pathway is glucose 6-phosphate, but XP can also be formed by direct phosphorylation of D-xylulose with li-xylulokinase. Tritsch et al. [114] developed a radiometric test system for the measurement of D-xylulose kinase (XK) activity in crude cell extracts. Aliquots were spotted onto silica plates and developed in n-propyl alcohol-ethyl acetate-water (6 1 3 (v/v) to separate o-xylose/o-xylulose from XP. Silica was scraped off and determined by liquid scintillation. The conversion rate of [ " C]o-xylose into [ " C]o-xylulose 5-phosphate was calculated. Some of the works devoted to the separation of components necessary while analyzing enzyme activity are presented in Table 9.8. 

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