Fluoride inhibition

The permanganate oxidation of phenols is complicated by the intervention of lower oxidation states of manganese, (c/. the oxidation of toluene, p. 298). For example, the oxidation of 2,6-dinitrophenol in weakly acidic solution displays an induction period, following second-order kinetics thereafter. However, addition of potassium fluoride inhibits reaction almost completely, but manganous ions strongly accelerate it. 

Deutsch DG, Lin S, Hill WAG, Morse KL, Salehani D, Arreaza G, Omeir RL, Makriyannis A. Fatty acid sulfonyl fluorides inhibit anandamide metabolism and bind to the cannabinoid receptor. Biochem Biophys Res Com-mun 1997 231 217-221. 

Epp MA, Chanton JP. 1993. Rhizospheric methane oxidation determined via the methyl-fluoride inhibition technique. Journal of Geophysical Research-Atmospheres 98 18413-18422. 

Vinyl Fluoride, Inhibited Fluosilicic Acid Fluosulfonic Acid Fluosulfonic Acid Calcium Fluoride Fluosilicic Acid Calcium Fluoride Fluosulfonic Acid... 

VINYL FLUORIDE, INHIBITED Fiuoroethylene, Monofiuoro-ethylene Flammable Compressed Gas 4 2... 

Vinylidene fluoride is taken up rapidly via the pulmonary route in rats, but at equilibrium the mean concentration (by volume) in rats was only 23% of that in the gaseous phase. Metabolism proceeded very slowly and was saturable at exposure concentrations of about 260 mg/m Its maximum rate was 1% that of vinyl chloride and less than 20% that of vinyl fluoride there has been a report of an increase in the urinary excretion of fluoride in exposed rats. No alkylating intermediate was demonstrated after passage through a mouse-liver microsomal system. However, vinylidene fluoride inhibits mixed-function oxidase activity in vitro and, like similar halogenated compounds that are transformed to reactive metabolites, it alters rat intermediary metabolism, leading to acetone exhalation (lARC, 1986). 

Bacteria on the surface of our teeth metabolize sugars to produce lactic acid, which lowers the pH enough to slowly dissolve tooth enamel. Fluoride inhibits tooth decay because it forms fluorapatite, Cal0(PO4)6F2, which is more acid resistant than hydroxyapatite. 

Reiner and his colleagues (40) demonstrated that fluoride inhibition of prostatic acid phosphatase showed interesting and unexpectedly complex kinetics. The unusual nature of the inhibition can readily be appreciated from Fig. 4 (40). As the fluoride concentration is increased over a 1000-fold range, the extent of inhibition rises and then subsequently falls with a further increase of inhibitor. At lower fluoride concentration, the inhibition is clearly competitive. Two possibilities were explored for an explanation of these unusual concentration effects of inhibition. There could be two forms of fluoride in the reaction mixtures the inhibitory form and the second which predominates at higher... 

Vescia and Chance Hi) demonstrated that fluoride and tartrate inhibition vide infra) of acid phosphatase showed completely different kinetics when the hydrolysis of phenyl phosphate was compared with transphosphorylation from this substrate to glucose. Figures 5 and 6 (41) show that fluoride inhibition is competitive when the data are plotted according to Lineweaver and Burk. However, the inhibition is noncompetitive with respect to transphosphorylation of the same substrate to glucose. The authors suggested that there are two distinct sites... 

Seedlings are a rich source for nonspecific acid phosphatase. Newmark and Wenger (114) have reported on a 1000-fold purification from lupine seedlings. The purified enzyme hydrolyzes phosphate monoesters and pyrophosphate with p-nitrophenyl phosphate as substrate. The optimal activity was at pH 5.2-5.5, and Km was 3 X 10 4 M. Fluoride inhibition was noncompetitive. 

Sulfonyl Fluorides. Sulfonyl fluorides inhibit serine proteases by reacting with the active-site serine residue. Previously we investigated the rates of inhibition of human leukocyte elastase and cathepsin G by a variety of sulfonyl fluorides and found relatively little selectivity or reactivity (38). However, we have discovered recently that the introduction of fluoroacyl groups into the sulfonyl fluoride structure gives considerable reactivity and selectivity for elastase (39). 

An alternative scenario was put forward based on the crystal structures of urease inhibited by either phosphate, diamidophosphate, or borate (4,5, 28). It gets some support from the kinetic findings for fluoride inhibition of urease (29), as well as from recent model calculations (30, 31). Boric acid, known to be a competitive inhibitor of urease, can be considered a good substrate analogue, since it is isoelectronic with urea and has the same shape and dimension. Bacillus pasteurii could be crystallized in the presence of boric acid. The structure reveals that a molecule of B(OH)3 is symmetrically spanning the nickel ions, replacing Wj, W2,... 

In addition, urease is inhibited by a variety of agents including fluoride and disulfldes, as observed recently in the acetohydroxamate-inhibited C319A variants of K. aero-genes urease. It is proposed that this mode of inhibition involves coordination of the inhibitor to only one nickel center, while another involves the inhibitor bridging the dinickel center. Urease is slowly inhibited by fluoride in both the presence and absence of substrate, and fluoride binding rates are directly proportional to inhibitor concentration. Fluoride inhibition is pH-dependent due to a protonation... 

SYNS ETHENE, FLUORO- ETHYLENE, FLUORO-(8CI) FLUOROETHENE FLUOROETHYLENE MONOFLUOROETHYLENE VINYL FLUORIDE, inhibited pOT)... 

It is interesting to note that Volk et al. are able to differentiate between the two enzyme activities by the lack of fluoride inhibition of PPase II, which is in contradiction with the results in [20]. Volk et al. also obtained, though careful differentiation of mitochondrial membranes, a localization of the PPases. They came to the conclusion that PPase I is localized in the mitochondrial matrix. PPase II is situated in the inner mitochondrial membrane, a localization in line with its proposed role as a coupling factor [71]. 

For more than forty years, the potential for nephrotoxicity, particularly when fluoride induced, has influenced every aspect of the development of new inhaled anesthetics. This concern is based on the experience with methoxyflurane, which was introduced in the US in 1%0 [89]. The exact mechanism(s) responsible for fluoride nephrotoxicity have not been defined. The fluoride ion interferes with normal cell function on several levels. Fluoride inhibits several cellular enzyme systems and diminishes tissue respiration and anaerobic glycolysis [90]. The lethal dose of sodium fluoride in humans is approximately 5 g [90]. In the kidney. 

Symptoms Gastric symptoms nausea, salivation, abdominal pain Direct effects of fluoride Inhibition of metabolism Persistent abnormal serum fluoride levels... 

Edwards, S.F., T.F. Poulos, and J. Kraut. 1984. The crystal structure of fluoride-inhibited cytochrome c peroxidase.. Biol. Chem. 259 12984—12988. 

Kamaluddin, M. and J.J. Zwiazk. 2003. Fluoride inhibit root water transport and affects leaf expansion ad gas exchange in aspen (Populus tremuloides) seedlings. Physiol. Plant. 117(3) 368-375. 

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