- Evaluation of Natural and Synthetic Phosphate Donors for the Improved Enzymatic Synthesis of Phosphate Monoesters
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Undesired product hydrolysis along with large amounts of waste in form of inorganic monophosphate by-product are the main obstacles associated with the use of pyrophosphate in the phosphatase-catalyzed synthesis of phosphate monoesters on large scale. In order to overcome both limitations, we screened a broad range of natural and synthetic organic phosphate donors with several enzymes on a broad variety of hydroxyl-compounds. Among them, acetyl phosphate delivered stable product levels and high phospho-transfer efficiency at the lower functional pH-limit, which translated into excellent productivity. The protocol is generally applicable to acid phosphatases and compatible with a range of diverse substrates. Preparative-scale transformations using acetyl phosphate synthesized from cheap starting materials yielded multiple grams of various sugar phosphates with up to 433 g L?1 h?1 space-time yield and 75% reduction of barium phosphate waste. (Figure presented.).
- Tasnádi, Gábor,Jud, Wolfgang,Hall, Mélanie,Baldenius, Kai,Ditrich, Klaus,Faber, Kurt
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supporting information
p. 2394 - 2401
(2018/05/14)
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- METHOD FOR THE ENZYMATIC PRODUCTION OF D-ERYTHROSE AND ACETYL PHOSPHATE
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Described is a method for the production of D-erythrose and acetyl phosphate comprising the enzymatic conversion of D-fructose into D-erythrose and acetyl phosphate by making use of a phosphoketolase. The produced D-erythrose can further be converted into glycolaldehyde by a method for the production of glycolaldehyde comprising the enzymatic conversion of D-erythrose into glycolaldehyde by making use of an aldolase, wherein said aldolase is a 2- deoxyribose-5-phosphate aldolase (EC 4.1.2.4) or a fructose-bisphosphate aldolase (EC 4.1.2.13). The produced glycolaldehyde can finally be converted into acetyl phosphate by the enzymatic conversion of the thus produced glycolaldehyde into acetyl phosphate by making use of a phosphoketolase or a sulfoacetaldehyde acetyltransferase.
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Page/Page column 41-44
(2015/12/17)
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- Cloning, expression, purification, cofactor requirements, and steady state kinetics of phosphoketolase-2 from Lactobacillus plantarum
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The genes xpk1 and xpk2(Δ1-21) encoding phosphoketolase-1 and (Δ1-7)-truncated phosphoketolase-2 have been cloned from Lactobacillus plantarum and expressed in Escherichia coli. Both gene-products display phosphoketolase activity on fructose-6-phosphate in extracts. A N-terminal His-tag construct of xpk2(Δ1-21) was also expressed in E. coli and produced active His-tagged (Δ1-7)-truncated phosphoketolase-2 (hereafter phosphoketolase-2). Phosphoketolase-2 is activated by thiamine pyrophosphate (TPP) and the divalent metal ions Mg2+, Mn2+, or Ca2+. Kinetic analysis and data from the literature indicate the activators are MgTPP, MnTPP, or CaTPP, and these species activate by an ordered equilibrium binding pathway, with Me2+TPP binding first and then fructose-6-phosphate. Phosphoketolase-2 accepts either fructose-6-phosphate or xylulose-5-phosphate as substrates, together with inorganic phosphate, to produce acetyl phosphate and either erythrose-4-phosphate or glyceraldehyde-3-phosphate, respectively. Steady state kinetic analysis of acetyl phosphate formation with either substrate indicates a ping pong kinetic mechanism. Product inhibition patterns with erythrose-4-phosphate indicate that an intermediate in the ping pong mechanism is formed irreversibly. Background mechanistic information indicates that this intermediate is 2-acetyl-TPP. The irreversibility of 2-acetyl-TPP formation might explain the overall irreversibility of the reaction of phosphoketolase-2.
- Yevenes, Alejandro,Frey, Perry A.
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p. 121 - 127
(2008/09/20)
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- Dissection of Nucleophilic and General Base Roles for the Reaction of Phosphate with p-Nitrophenyl Thiolacetate, p-Nitrophenyl Thiolformate, and Phenyl Thiolacetate
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Phosphate buffers are well-known to catalyze the decomposition of various active acyl compounds. This study was undertaken to determine the extent to which it acts as a nucleophile and general base toward some activated esters and thiolesters. Thus, the hydrolyses of p-nitrophenyl acetate (3a), p-nitrophenyl thiolacetate (3b), phenyl acetate (4a), phenyl thiolacetate (4b), and p-nitrophenyl thiolformate (5) have been studied in aqueous phosphate, μ = 1.0 (K2SO4). Both phosphate monoanion and dianion are reactive toward the thiolesters 3b, 4b, and 5. For 3b, reaction of the dianion exhibits a solvent kinetic isotope effect (SKIE) of 1.00 ± 0.11 while that for the monoanion is 2.13 plusmn; 1.1. For the reaction of phosphate dianion with 5, the SKIE is 0.8 ± 0.2 and that for the monoanion at pH 3.05 is roughly 1.5. Phosphate dianion reacts with each thiolacetate and its oxygen analogue at comparable rates: the reactivity ratio of the formyl to acetyl thiolesters, 5:3b, toward phosphate dianion is 685. 1H NMR analysis of the 3b hydrolysis mixtures in H2O and D2O containing phosphate shows the transient formation, and subsequent hydrolysis, of acetyl phosphate. Analysis of the kinetics of these processes indicates that in H2O at pH = 8.5, phosphate dianion functions as both a nucleophile and general base toward 3b, the nucleophilic role comprising 80-93% of the reaction. In D2O, the process is entirely nucleophilic. For the reaction of phosphate dianion with 4b, the 1H NMR analysis indicates that the nucleophilic role comprises 40-50% of the reaction, the general base role being 50-60%. The reaction of phosphate dianion with 5 is entirely nucleophilic, while the monoanion reacts as a general base. The data are interpreted in terms of standard carbonyl addition/elimination mechanisms in which the ability of the attacking phosphate di- or monoanion to displace a given leaving group is tied to the pKa of the conjugate acids of the nucleophile and leaving groups.
- Gill, Manjinder S.,Neverov, Alexei A.,Brown
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p. 7351 - 7357
(2007/10/03)
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- Nucleophilic Reactivity toward Acetyl Chloride in Water
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Rate constant ratios for the reactions of acetyl chloride with nucleophilic reagents in water containing 2.5percent (v/v) dioxane were determined by product analysis.The rate constants show a small dependence on the basicity of primary amines, with βnuc=0.25, and are assigned to rate-limiting attack of the nucleophile.Pyridines with pKa>5 behave similarly, with βnuc=0.24, but less basic pyridines react more slowly.Several "α-effect" amines and anionic oxygen nucleophiles show small rate enhancements that are attributed to increases in the rate of nucleophilic attack.The rate constants do not fit the N+ correlation equation, and it is concluded that the reactions of nucleophilic reagents with acyl compounds are not satisfactorily correlated by simple modifications of this equation.
- Palling, David J.,Jencks, William P.
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p. 4869 - 4876
(2007/10/02)
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