Alcohol-bicarbonate-water system. Structure-reactivity studies on the equilibriums for formation of alkyl monocarbonates and on the rates of their decomposition in aqueous alkali

Sauers, Carol K.; Jencks, William P.; Groh, Susan E.

doi:10.1021/ja00852a038

Cited by 120 publications

(113 citation statements)

References 7 publications

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“…Alternatively, the UreDUreF-UreG-apourease complex might use GTP and bicarbonate (not CO 2 ) to synthesize carboxyphosphate. Although this molecule possesses a half-life of less than 70 ms when free in solution (22), if generated within the complex near the lysine undergoing carbamylation it could function as an excellent CO 2 donor. We used established methods (5) to try to distinguish if CO 2 or bicarbonate was the true substrate for the GTP-dependent activation of urease apoprotein in the UreDUreF-UreG-apourease complex.…”

Section: Resultsmentioning

confidence: 99%

GTP-dependent activation of urease apoprotein in complex with the UreD, UreF, and UreG accessory proteins

Soriano

Hausinger

1999

Proc. Natl. Acad. Sci. U.S.A.

116

157

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Syntheses of metal-containing enzymes often require the participation of accessory proteins. The roles played by many of these accessory proteins are poorly characterized. Klebsiella aerogenes urease, a nickel-containing enzyme, provides an ideal system to study metallocenter assembly. Here, we describe a method for isolating a complex containing urease apoprotein and the UreD, UreF, and UreG accessory proteins. We demonstrate that urease apoprotein in this complex is activated to near wild-type enzyme levels when incubated with nickel ions and high (Ϸ100 mM) concentrations of bicarbonate. Significantly, we also observed nickeldependent activation at physiologically relevant (Ϸ100 M) bicarbonate levels, but only in the presence of GTP. Based on studies involving a nonhydrolyzable analog of GTP, we conclude that nucleotide hydrolysis, not just binding, is required for this process. The critical nucleotide-binding site was localized to UreG on the basis of experiments using a variant complex. These studies highlight the relevance of the UreDUreF-UreG-urease apoprotein complex to nickel metallocenter assembly and explain the previously identified in vivo energy requirement for urease activation.

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Section: Resultsmentioning

confidence: 99%

GTP-dependent activation of urease apoprotein in complex with the UreD, UreF, and UreG accessory proteins

Soriano

Hausinger

1999

Proc. Natl. Acad. Sci. U.S.A.

116

157

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“…Although more stable than the corresponding acid, the salts readily react with water [2,8,11,12]. The kinetic and equilibrium constants obtained in these works suggest that several MACs could be obtained from an alcohol and bicarbonate in aqueous medium (Scheme 1).…”

Section: Introductionmentioning

confidence: 87%

Investigating the formation and the properties of monoalkyl carbonates in aqueous medium using capillary electrophoresis with capacitively coupled contactless conductivity detection

et al. 2011

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Although alkyl carbonic acids (ACAs) and their salts are referred to as instable species in aqueous medium, we demonstrate that a monoalkyl carbonate (MAC) can in fact be easily formed from bicarbonate and an alcohol even in the presence of a high amount of water. A CE system with two capacitively coupled contactless conductivity detectors (C⁴Ds) was used to obtain different parameters about these species and their reactions. Based on the mobilities obtained for a series of alcohols ranging from 1 to 5 carbons, the coefficients of diffusion and the hydrodynamic radii were calculated. When compared with the equivalent carboxylates, MACs have radii systematically smaller. Although the precise pK(a) values of the ACAs could not be obtained, because of the fast decomposition in acid medium, it was possible, for the first time, to show that they are below 4.0. This result suggests that the acidity of an ACA is quite similar to the first hydrogen of H₂CO₃. Using a new approach to indirectly calibrate the C⁴D, the kinetic constants and the equilibrium constants of formation were also obtained. The results suggest that the increase in the chain length makes the MACs less stable and more inert.

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“…Although the rate of decarboxylation, k dec , cannot be measured in the present system, it can be estimated from published studies of similar reactions. The decarboxylation rate (k dec ) of carbonate monoesters has been shown to follow the relationship: log(k dec ) ϭ 15.1 Ϫ 1.16pK a , where pK a is the pK a of the hydroxyl group that is esterified to the carbonate (34,35). Because the pK a of DBHQ is estimated to be 11.21 (36), the rate constant for decomposition of the carbonate monoester of DBHQ is expected to be k dec Ϸ 130 s Ϫ1 (t1 ⁄2 Ϸ 5.3 ms) at 25°C.…”

Section: Nmoc-dbhq: Caged Inhibitor For Photomodulation Of Ca 2ϩ Pumpmentioning

confidence: 99%

Nmoc-DBHQ, a New Caged Molecule for Modulating Sarcoplasmic/Endoplasmic Reticulum Ca2+ ATPase Activity with Light Flashes

Rossi

Kao

1997

Journal of Biological Chemistry

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We report the synthesis and characterization of O-[o-nitromandelyloxycarbonyl]-2,5-di(tert-butyl)hydroquinone (Nmoc-DBHQ), a new "caged" reagent for photoreleasing DBHQ, a membrane-permeant, reversible inhibitor of the sarcoplasmic/endoplasmic reticulum Ca 2؉ ATPase (SERCA). The Nmoc group is a new caging group developed for the current application. Photolysis of Nmoc-DBHQ proceeds with t1 ⁄2 ‫؍‬ 126 ؎ 2 s, and t1 ⁄2 for subsequent release of DBHQ is estimated to be ϳ5 ms. Nmoc-DBHQ thus allows rapid and reversible modulation of SERCA activity in living cells. Through its acetoxymethyl ester, Nmoc-DBHQ can be loaded into cells easily by incubation. We demonstrate the use of Nmoc-DBHQ for photomodulating SERCA activity in fibroblasts and vagal sensory neurons. We further demonstrate the utility of pulsed DBHQ photorelease for probing and manipulating dynamic phenomena such as [Ca 2؉ ] oscillations in fibroblasts.Intracellular concentration and distribution of the ubiquitous second messenger Ca 2ϩ is tightly controlled by a number of pathways (1). The interaction of the pathways that mobilize and regulate free Ca 2ϩ levels can result in highly complex and dynamic signaling patterns, such as Ca 2ϩ oscillations and waves (1-3). Pulsed perturbation of the concentrations of various second messengers, achieved by flash photolysis of caged inositol-1,4,5-trisphosphate, diacylglycerol, and Ca 2ϩ (4 -8), has yielded highly specific mechanistic information about these dynamic phenomena (5, 9). Although the role of second messengers themselves in dynamic signaling phenomena has been studied by photorelease techniques, the contribution of pathways that regulate second messenger levels remains unexplored.The family of sarcoplasmic/endoplasmic reticulum Ca 2ϩ ATPases (SERCA) 1 that sequester Ca 2ϩ into the sarcoplasmic reticulum and endoplasmic reticulum are important regulators of cytosolic free Ca 2ϩ levels (10). We reasoned that the effect of these pumps on Ca 2ϩ oscillations and waves could be elucidated by the development of a method for the pulsed modulation of their activity. This could be accomplished by the preparation of a caged, reversible SERCA inhibitor. Of the known SERCA inhibitors (11), 2,5-di(tert-butyl)-1,4-hydroquinone (DBHQ, 1) (12, 13) is ideally suited for the development of a caged SERCA modulator because it is a structurally simple and reversible inhibitor that is commercially available in large quantities. EXPERIMENTAL PROCEDURESSynthesis-Reagents and solvents were ACS or high pressure liquid chromatography grade and were used as received from Aldrich or Fisher. Dimethylformamide and dichloromethane were stored over 3 Å molecular sieves. All oxygen-and water-sensitive reactions were performed under dry argon atmosphere. For water-sensitive reactions, glassware was dried at 130°C for at least 3 h and cooled under a stream of argon or in a desiccator prior to use. Silica gel 60 (230 -400 mesh, Merck) was used for column chromatography. Melting points were recorded on a Melt-temp II (Laboratory Devic...

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Alcohol-bicarbonate-water system. Structure-reactivity studies on the equilibriums for formation of alkyl monocarbonates and on the rates of their decomposition in aqueous alkali

Cited by 120 publications

References 7 publications

GTP-dependent activation of urease apoprotein in complex with the UreD, UreF, and UreG accessory proteins

GTP-dependent activation of urease apoprotein in complex with the UreD, UreF, and UreG accessory proteins

Investigating the formation and the properties of monoalkyl carbonates in aqueous medium using capillary electrophoresis with capacitively coupled contactless conductivity detection

Nmoc-DBHQ, a New Caged Molecule for Modulating Sarcoplasmic/Endoplasmic Reticulum Ca2+ ATPase Activity with Light Flashes

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