Labile phosphate

As bacterial transglucosidase is instrumental in the transfer of a D-glucose residue from one acceptor to another, so does yeast hexokinase 3 catalyze a transphosphorylation. The highly specific donator of a labile phosphate group is adenosine triphosphate (XX), the fermentable hexoses D-glucose, D-mannose and D-fructose functioning as acceptors. Hexokinase catalyzes the reaction... 

Fmoc-Based Solid-Phase Synthesis of Phosphotyrosine-Containing Peptides via Acid-Labile Phosphate Alkyl Ester Protection... 

A major advancement in the Fmoc-based solid-phase synthesis of Tyr(P)-peptides was realized with the Fmoc-Tyr[PO(OR1)2]-OH derivatives 7 (R1 = Bzl, tBu, Mdpse) [Mdpse = 2-(methyldiphenylsilyl)ethyl] in which the acid-labile phosphate esters offered simple cleavage by TFA treatment. While the initial difficult synthesis of derivatives 7 restricted general synthetic usage, the subsequent commercial availability of these derivatives and their compatibility with solid-phase synthesis has provided a simple and efficient procedure for the routine synthesis of large complex Tyr(P)-peptides. 

Synthesis of Acid-Labile Phosphate Alkyl Ester Derivatives of Fmoc-Protected... 

Solid-Phase Synthesis of Phosphotyrosine Peptides with Acid-Labile Phosphate... 

Most of the compounds under discussion are quite labile in acid, but with two important exceptions they are resistant to mild alkaline hydrolysis (0.1-1 N base, 25°C). One exception is the mixed anhydrides of phosphate and carboxylic acids, such as acetyl phosphate. They are very susceptible to alkaline cleavage or cleavage by nucleophiles such as hydroxylamine. The other relatively alkali-labile phosphate compounds are phosphodiesters, in which the phosphate is attached to one of two vicinal hydroxyl groups (as in RNA or derivatives of phosphatidic acid). In these instances, the neigh-... 

The slow, post-irradiation decrease in viscosity ( after-effect ) was investigated by Daniels, Scholes, Weiss, and Wheeler, who relate this phenomenon to the labilization of phosphate bonds by the intermediate formation of labile phosphate esters. Leading to this conclusion is the observation that about fifteen times as much inorganic phosphate can be obtained by acid hydrolysis of irradiated, aqueous solutions of nucleic acid as is formed directly by the radiation. It is, therefore, thought that, after the labile phosphate esters have been formed, they undergo slow acid hydrolysis, and that this mild hydrolysis occurring at the diester phosphate groups, even... 

Related to the interpretation of the effects of radiation on nucleic acids are the studies on the formation of labile phosphate esters in solutions of simple phosphates by irradiation. When glyceritol 1- and 2-phosphates are irradiated with 200 KV x-rays, inorganic phosphate is liberated. The former gives l,3-dihydroxy-2-propanone phosphate, and the latter, an acid-labile phosphate ester. " Detailed studies on methyl, ethyl, propyl, butyl, and amyl phosphates have indicated the mode of formation of such labile phosphate esters. Two reactions have been recognized ... 

D-glucosamine preparation. This labile phosphate derivative is inactive as a substrate. Since the d anomer of D-glucosyl phosphate is more acid-labile than is the a anomer/ the a anomer of iV-acetyl-D-glucosamine 1-phosphate is considered to be involved in this reaction. ... 

Hepatic glycogen synthase is similar to the muscle enzyme, although it is encoded by different genes. It is inactivated by phosphorylation and activated by dephosphorylation and may contain 12 mol of alkali-labile phosphate per mole of subunit. The phosphorylation sites have not been mapped, and the specificities of hepatic glycogen synthase kinases are not known. 

A substance class of particular importance as intermediates in most central metabolic processes and also as chemical messengers in many signal cascades are organophosphates [64], Despite of their pivotal biochemical role they are often only short-lived species which are rapidly hydrolyzed either spontaneously or by ubiquitous phosphatases. To make use of phosphates as bioactive compounds of pharmaceutical interest, the hydrolytically labile phosphate bond has to be stabilized [65]. 

Carbohydrate SVI titrated as a monobasic acid, pK = 2.0, as expected for a phosphate diester, - and mild alkaline hydrolysis cleaved the labile, phosphate diester linkage, to produce a serologically inert monoester, [a]D -M06°, which was not precipitated by alcohol in the presence of calcium acetate. Acidic or enzymic hydrolysis of the monoester yielded a crystalline, nonreducing, chromatographically homogeneous tetrasaccharide which, after sequential methylation and acidic hydrolysis, yielded 2,3,4,6-... 

G-Actin solutions contain small, variable amounts of ATP (Straub and Feuer, 1950 Dubuisson and Mathieu, 1950 Laki et al., 1950 Mommaerts, 1951a). After deproteinization, ATP has been determined (a) by its effect on actomyosin solution, (b) elementary analysis of the isolated substance (Straub and Feuer, 1950), (c) by the determination of labile phosphate (Dubuisson and Mathieu, 1950), (d) by ultraviolet absorption (Laki et al., 1950 Mommaerts, 1951a), and (e) by reduction of coenzyme II. 

The prevalence of highly weathered soils in the tropics makes organic phosphorus potentially more important for plant availability than in temperate soils. The relationships between chemically extracted phosphorus fractions in 168 soils suggested that labile phosphate is derived mainly from stable soil phosphate fractions in slightly... 

Oestreich and Jones (1967) have studied the role of magnesium and calcium ions in the hydrolysis of various labile phosphate compounds. Infrared and NMR data on D2O solutions of acetyl phosphate and magnesium sulfate showed no characteristics which could be assigned to chelate structures (in the group state) involving the carbonyl group, as in CXXll ... 

Forms by Dictyostelium discoideum Journal of Biological Chemistryy 257, 9861-5 Park, J.T. Johnson, M.J. (1949) Accumulation of Labile Phosphate in Staphylococcus aureus Grown in the Presence of Penicillin , Journal of Biological Chemistry, 179, 585-92 Park, J.T. Strominger, J.L. (1957) Mode of Action of Penicillin , Science, 125, 99-101 Paro, A.J. (1976) Protein Glycosylation Through Dolichol Derivatives in Baker s Yeast , FEBS Letters, 71, 283-6... 

Phosphate esters are usually synthesized by means of phosphoiylating transferases called kinases, which catalyze the transfer of a phosphate moiety (or a di- ° or triphosphate moiety) from an energy-rich phosphate donor, such as ATP. Due to the high price of these phosphate donors, they cannot be employed in stoichiometric amounts. Since ATP cannot be replaced by less expensive man-made chemical equivalents, efficient in-situ regeneration (i.e., recycling) is necessary in order to reduce the cost of enzymatic phosphorylations. Fortunately, ATP recycling has become feasible on a molar scale [520, 521]. On the other hand, reversal of phosphate ester hydrolysis, i.e., the equivalent condensation reaction, has been performed in solvent systems with a reduced water content. Such systems would eliminate the use of expensive or chemically labile phosphate-donors but it is questionable if they will be of general use [522]. 

Another labile phosphate species, which is needed as a cosubstrate for DHAP-dependent aldolase reactions, is dihydroxyacetone phosphate (Scheme 2.83, also see Sect. 2.4.1). Its chemical synthesis using phosphorus oxychloride is hampered by moderate yields. Enzymatic phosphorylation, however, gives significantly enhanced yields of a product which is sufficiently pure so that it can be used directly in solution without isolation [541, 542]. 

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