The crystal structure of rubidium ammonium hydrogen fluorocitrate dihydrate

Carrell, H. L.; Glusker, Jenny P.

doi:10.1107/s0567740873003158

Cited by 11 publications

(3 citation statements)

References 8 publications

(8 reference statements)

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“…There is only a very small number of crystal structures which display short CF···Rb + contacts. Two of these have biological relevance: Fluorocitrate, whose rubidium−hydrogen−ammonium salt has CF···Rb + contacts of 297.9(5) and 309.5(4) pm (FLUCIT) is highly toxic due to the deactivation of aconitase . Derivatives of the rubidium salt of 5-fluoro-orotate monohydrate [CF···Rb + 288.0, 321.5 pm, RBFORM] are used in cancer treatment …”

Section: Rubidiummentioning

confidence: 99%

The Coordination Chemistry of the CF Unit in Fluorocarbons

1997

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ContentsI. Introduction 3363 II. Scope of This Review 3364 III. Complexes of the Alkali and Alkaline Earth Metal Ions 3365 A. Lithium 3365 B. Sodium 3367 C. Potassium 3368 D. Rubidium 3369 E. Cesium 3369 F. Distribution Statistics of the CF‚‚‚Metal Distances 3370 G. Calcium, Strontium, and Barium 3371 H. Complexes of the Fluoro Macrocycles in Solution 3371 I. Stereoselective Synthesis Using CF Donors as Directing Groups 3372 IV. Complexes of the Transition Metals Including Zn, Cd, Hg 3373 A. First Row Transition Elements Sc−Zn 3373 B. Second Row Transition Elements Y−Cd 3374 1. Zirconium 3374 2. Silver 3375 3. Other Second Row Transition Elements 3376 C. Third Row Transition Elements La−Hg 3377 V. Complexes of the Lanthanides and Actinides 3377 VI. Complexes of the Main Group Metals 3377 A. Gallium and Indium 3378 B. Thallium 3378 C. Germanium, Tin, Lead, and Bismuth 3379 VII. On the Possibility of CF‚‚‚HN and CF‚‚‚HO Hydrogen Bonds 3379 VIII. Recurring Structural Motifs in the Coordination Chemistry of the CF Unit and Concluding Remarks 3380 IX. Acknowledgments 3381 X. References and Notes 3381

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Section: Rubidiummentioning

confidence: 99%

The Coordination Chemistry of the CF Unit in Fluorocarbons

1997

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“…From crystallographic data (Carrel and Glusker, 1973) Mn2+ to carbon distances of 2.8-3.2 Á would be expected for carboxylate and carbinol coordination by Mn2+. Hence, the distances of 2.93 and 2.71 Á calculated for the binary complex indicate bidentate coordination or chelation of Mn2+ by both the carboxylate and hydroxyl groups of mandelate (Figure 6).…”

Section: Morganmentioning

confidence: 99%

Mandelate racemase. V. Mandelate racemase from Pseudomonas putida. Magnetic resonance and kinetic studies of the mechanism of catalysis

Maggio¹,

Kenyon²,

Mildvan³

et al. 1975

Biochemistry

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The interactions of mandelate racemase with divalent metal ion, substrate, and competitive inhibitors were investigated. The enzyme was found by electron paramagnetic resonance (EPR) to bind 0.9 Mn2+ ion per subunit with a dissociation constant of 8 muM, in agreement with its kinetically determined activator constant. Also, six additional Mn2+ ions were found to bind to the enzyme, much more weakly, with a dissociation constant of 1.5 mM. Binding to the enzyme at the tight site enhances the effect of Mn2+ on the longitudinal relaxation rate (1/T1p) of water protons by a factor of 11.9 at 24.3 MHz. From the frequency dependence of 1/T1p, it was determined that there are similar to 3 water ligands on enzyme-bound Mn2+ which exchange at a rate larger than or equal to 10-7 sec-1. The correlation time for enzyme-bound Mn2+-water interaction is frequency-dependent, indicating it to be dominated by the electron spin relaxation time of Mn2+. Formation of the ternary enzyme-Mn2+-mandelate complex decreases the number of fast exchanging water ligands by similar to 1, but does not affect tau-c, suggesting the displacement or occlusion of a water ligand. The competitive inhibitors D,L-alpha-phenylglycerate and salicylate produce little or no change in the enzyme-Mn2+-H2O interaction, but ternary complexes are detected indirectly by changes in the dissociation constant of the enzyme-Mn2+ complex and by mutual competition experiments. In all cases the dissociation constants of substrates and competitive inhibitors from ternary complexes determined by magnetic resonance titrations agree with K-M and K-i values determined kinetically and therefore reflect kinetically active complexes. From the paramagnetic effects of Mn2+ on 1/T1 and 1/T2 of the 13C-enriched carbons of 1-[13C]-D,L-mandelate and 2-[13C]-D,L-mandelate, Mn2+ to carboxylate carbon and Mn2+ to carbinol carbon distances of 2.93 plus or minus 0.04 and 2.71 plus or minus 0.04 A, respectively, were calculated, indicating bidentate chelation in the binary Mn2+-mandelate complex. In the active ternary complex of enzyme, Mn2+, and D,L-mandelate, these distances increase to 5.5 plus or minus 0.2 and 7.2 plus or minus 0.2 A, respectively, indicating the presence of at least 98.9% of a second sphere complex in which Mn2+, and C1 and C2 carbon atoms are in a linear array. The water relaxation data suggest that a water ligand is immobilized between the enzyme-bound Mn2+ and the carboxylate of the bound substrate. This intervening water ligand may polarize or protonate the carboxyl group. From 1/T2p the rate of dissociation of the substrate from this ternary complex (larger than or equal to 5.6 times 10-4 sec-1) is at least 52 times greater than the maximal turnover number of the enzyme (1070 sec-1), indicating that the complex detected by nuclear magnetic resonance (NMR) is kinetically competent to participate in catalysis. Relationships among the microscopic rate constants are considered.

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“…Synthesis of malyl-glutathione thioester by inner membrane vesicles is selectively inhibited by (-)erythrofluoromalate. We have previously identified the biologically active species of the four possible isomers of monofluorocitric acid as (-)erythrofluorocitrate (1, 2); its structure subsequently was confirmed by x-ray crystallography (3,4). Kinetic evidence indicated that (-)erythrofluorocitrate, when preincubated with isolated mitochondria at concentrations of pmol of fluorocitrate per mg of mitochondrial protein, irreversibly inhibited bidirectional citrate transport (5)(6)(7)(8).…”

mentioning

confidence: 99%

Enzymatic formation of glutathione-citryl thioester by a mitochondrial system and its inhibition by (-)erythrofluorocitrate

Kun

Kirsten

Sharma

1977

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

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A soluble extract of the mitochondrial compartment composed of the inner membrane and matrix catalyzes the enzymatic synthesis and hydrolysis of the 1:1 adduct of citric acid and glutathione. (9) was also explained by the stringent requirement of preincubation of mitochondria with fluorocitrate in the absence of millimolar concentrations of citrate (cf. 7, 8), allowing for the formation of two protein-fluorocitrate thioesters (8).The present report is concerned with the identification of a mitochondrial enzyme system that catalyzes the formation of the 1:1 adduct of glutathione and citric acid. The adduct was identified as the thioester of glutathione, and kinetic evidence was also obtained that the mitochondrial extract contained, in addition to the thioester-forming enzyme system, a hydrolase capable of degrading the thioester. The citryl-glutathioneforming enzyme system proved to be the most sensitive catalytic component of mitochondria towards the irreversible inhibitory action of (-)erythrofluorocitrate, suggesting that the molecular site of action of this highly toxic agent has been identified. METHODSLysosome-free mitochondria and mitoplasts (defined as the matrix surrounded by the inner membrane) were isolated from rat livers as described (12). An extract of mitoplasts was prepared by stirring (at 00) of a suspension of mitoplasts (30 mg of protein per ml) in 0.25 M sucrose/mannitol medium (12) containing 1 mg of Brij 56 (Sigma Chemicals) per 10 mg of mitoplast protein for 15 min. The resulting lysate was diluted 1:3 with the medium; after removal of large granules (unbroken mitoplasts) by centrifugation at 10,000 X g (10 min at 40), the supernatant (containing soluble extract of the inner membrane and soluble proteins of the matrix and inner membrane vesicles) was subjected to ultracentrifugation (145,000 X g for 1 hr at 20). The clear supernatant was concentrated by centrifugation (at 20) in Amicon CF-25 membrane cones at 100 X g to one-fourth of the original volume. Approximately 250 mg of protein extract was obtained by this technique from 500 mg (protein) of mitoplast starting material. The concentrated extract was used directly in most experiments, unless specified, whereas the sediment containing the inner membrane vesicles was rehomogenized in the suspending medium. Both fractions were stored at -15°until used. The enzymatic activity of the soluble extract decayed slowly at -150 (about half of the activity was lost in 2 weeks) but much more rapidly after repeated thawing and refreezing. The activity was completely recovered when the stored extract was preincubated for 5-10 min with 5 mM reduced glutathione (GSH), demonstrating the essential role Abbreviations: GSH, reduced glutathione; GSSG, oxidized glutathione; Hepes, N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid; citryl-SG and malyl-SG, glutathione thioesters of citric and malic acids, respectively. 4942

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The crystal structure of rubidium ammonium hydrogen fluorocitrate dihydrate

Cited by 11 publications

References 8 publications

The Coordination Chemistry of the CF Unit in Fluorocarbons

The Coordination Chemistry of the CF Unit in Fluorocarbons

Mandelate racemase. V. Mandelate racemase from Pseudomonas putida. Magnetic resonance and kinetic studies of the mechanism of catalysis

Enzymatic formation of glutathione-citryl thioester by a mitochondrial system and its inhibition by (-)erythrofluorocitrate

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