Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.1.8 (cholinesterase)
 12,691 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The disposition of the organophosphate anticholinesterase, diisopropylfluorophosphate (DFP), was studied in guinea pigs after inhalation exposure. The tissue disposition of [3H]DFP and its metabolites was determined in the major tissues of the guinea pig from 5 min to 24 hr after treatment. [3H]DFP rapidly penetrated all tissues, where it was quickly hydrolyzed to the inactive metabolite, free [3H]diisopropylphosphoric acid ([3H]DIP), or was covalently bound to tissue in the form of bound [3H]DIP. Tissue concentrations of [3H]DFP and free [3H]DIP followed a biphasic curve, with an initial phase representing a very rapid decrease in tissue concentrations, followed by a slower phase of tissue clearance. Concentrations of free [3H]DIP generally exceeded those of [3H]DFP; however, by 4 hr the greater portion of the radioactivity in all the tissues was in the form of bound [3H]DIP. Bound [3H]DIP levels did not follow a biphasic clearance curve and declined at a slower rate than [3H]DFP and free [3H]DIP tissue levels. By 5 min the greatest accumulation of bound [3H]DIP occurred in the liver (nearly 20% of the total body burden), with a noticeably small amount in the brain (0.1%). Tissue concentrations of nonextractable radioactivity, thought to be [3H]monoisopropylphosphoric acid ([3H]MIP), were appreciable and persistent throughout the time course. Total cholinesterase activity in the brain and red blood cells was inhibited by about 90%, with plasma pseudo- and true cholinesterase activity inhibited by 99 and 97%, respectively. The time course of recovery of enzyme activity in these tissues failed to correlate with the respective tissue levels of either bound [3H]DIP or [3H]MIP.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The disposition of [3H]diisopropylfluorophosphate in guinea pigs after inhalation. 290 19

All employees of a chemical plant division producing chlorfenvinphos were studied, i.e. 35 males aged 25-57 years (mean 42.1); their employment period ranged from 1-15 years (mean 9.0). Chronic bronchitis was diagnosed in 13 workers (37.1%). Mean air chlorfenvinphos concentrations in the work environment estimated with gas-liquid chromatography were from 0.0008-0.0018 mg/m3 (maximum allowable concentration according to Polish standards is 0. 01 mg/m3). The activity of erythrocyte acetylcholinesterase was similar to that observed in people who were not exposed to chemicals, however, a slightly lowered activity of plasma cholinesterase in the studied population was evidently the result of mild liver impairment. Spirometric investigations performed in the studied workers revealed slight alterations manifested by increased intrathoracic gas volume (ITGV) (the value of the index was 138.6% of the mean value, 24 workers with an abnormally high index), as well as by decreased specific airway conductance (sGaw); its mean value in the studied group was 58.5% of the mean standard (11 people showed an abnormal index). Substantial functional changes were found in the respiratory muscles. Maximal inspiratory pressures (MIP = 97. 2 +/- 28.3 cm H2O) as well as maximal expiratory pressures (MEP = 113.9 +/- 44.2 cm H2O) in the studied group were significantly lower (p < 0.01) as compared to those observed in the control group (MIP = 120.7 +/- 31.7; MEP = 154.4 +/- 40.2 cm H2O) of 22 males having similar cigarette smoking habit, without occupational exposure to chemicals. It was also found that the people who had worked for more than 10 years under conditions of exposure to chlorfenvinphos showed significantly lower (p < 0.05) values of maximal inspiratory pressure (87.2 +/- 28.06 cm H2O, n = 17) compared to the workers whose period of employment was shorter than 10 years (106.6 +/- 26.8 cm H2O, n = 18). The two groups were comparable with regard to age and smoking habits. The values of maximal expiratory pressures were similar in both groups. No essential disturbances in neuro-muscular transmission were observed; only in 3 workers (8.5%) the electrostimulating myasthenic test showed some disturbances in neuro-muscular transmission. It seems that respiratory muscles impairment in humans exposed to chlorfenvinphos results from changes in the metabolism and structure of muscles, and partly from lung hyperinflation.
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PMID:Impaired respiratory muscle function in chemical plant workers producing chlorfenvinphos. 1038 11

Wild-type human butyrylcholinesterase (BuChE) and Glu-197-->Asp and Asp-70-->Gly mutants (E197D and D70G respectively) were inhibited by di-isopropyl phosphorofluoridate under standard conditions of pH, temperature and pressure. The effect of hydrostatic and osmotic pressures on the aging process (dealkylation of an isopropyl chain) of phosphorylated enzymes [di-isopropylated (DIP)-BuChE] was investigated. Hydrostatic pressure markedly increased the rate of aging of wild-type enzyme. The average activation volume (DeltaV( not equal)) for the dealkylation reaction was -170 ml/mol for DIP wild-type BuChE. On the other hand, hydrostatic pressure had little effect on the aging of the DIP mutants (DeltaV( not equal)=-2.6 ml/mol for E197D and -2 ml/mol for D70G), suggesting that the transition state of the aging process was associated with an extended hydration and conformational change in wild-type BuChE, but not in the mutants. The rate of aging of wild-type and mutant enzymes decreased with osmotic pressure, allowing very large positive osmotic activation volumes (DeltaV not equal osm) to be estimated, thus probing the participation of water in the aging process. Molecular dynamics simulations performed on the active-site gorge of the wild-type DIP adduct showed that the isopropyl chain involved in aging was highly solvated, supporting the idea that water is important for stabilizing the transition state of the dealkylation reaction. Wild-type BuChE was inhibited by soman (pinacolyl methylphosphonofluoridate). Electrophoresis performed under high pressure [up to 2.5 kbar (1 bar=10(5) Pa)] showed that the soman-aged enzyme did not pass through a pressure-induced, molten-globule transition, unlike the native wild-type enzyme. Likewise, this transition was not seen for the native E197D and D70G mutants, indicating that these mutants are resistant to the penetration of water into their structure. The stability energetics of native and soman-aged wild-type BuChE were determined by differential scanning calorimetry. The pH-dependence of the midpoint transition temperature of endotherms indicated that the high difference in stabilization energy between aged and native BuChE (DeltaDeltaG=23.7 kJ/mol at pH 8.0) is mainly due to the salt bridge between protonated His-438 and PO(-), with pK(His-438)=8.3. A molecular dynamics simulation on the MIP adduct showed that there is no water molecule around the ion pair. The 'hydrostatic versus osmotic pressure' approach probed the importance of water in aging, and also revealed that Asp-70 and Glu-197 are the major residues controlling both the dynamics and the structural organization of the water/hydrogen-bond network in the active-site gorge of BuChE. In wild-type BuChE both residues function like valves, whereas in the mutant enzymes the water network is slack, and residues Gly-70 and Asp-197 function like check valves, i.e. forced penetration of water into the gorge is not easily achieved, thereby facilitating the release of water.
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PMID:Hydration change during the aging of phosphorylated human butyrylcholinesterase: importance of residues aspartate-70 and glutamate-197 in the water network as probed by hydrostatic and osmotic pressures. 1051 Mar 1

Elucidating mechanisms of aging of esterases inhibited by organophosphorus (OP) compounds is important for understanding toxicity and developing biomarkers of exposure to these agents. Aging has classically been thought to involve net loss of a single side group from the OP moiety of phosphylated esterases, rendering the enzyme refractory to reactivation. However, recent evidence has shown that acetylcholinesterase (AChE) and the catalytic domain of human neuropathy target esterase (NEST) undergo aging by alternative mechanisms following their inhibition with N,N'-diisopropylphosphorodiamidofluoridate (mipafox, MIP). This study was performed to determine whether MIP-inhibited butyrylcholinesterase (BChE) ages conventionally, by net loss of a single side group, or by an alternate route, e.g., reversible deprotonation or displacement of both isopropylamine groups, as recently observed for MIP-inhibited NEST and AChE, respectively. Diisopropylphosphorofluoridate (DFP), the phosphate analogue of the phosphoroamidate MIP, was used for comparison. Kinetic values for MIP against BChE were as follows: ki = (1.28 +/- 0.053) x 10(6) M-1 min-1; k3 = 0.004,15 +/- 0.000,27 min-1; k4 = 0.008,49 +/- 0.000,99 min-1. Kinetic values for DFP against BChE were as follows: ki = (1.83 +/- 0.18) x 10(6) M-1 min-1; k3 = 0.004,88 +/- 0.000,24 min-1; k4 = 0.0121 +/- 0.0028 min-1. Mass spectrometric studies revealed a mass shift of 123.4 +/- 0.7 Da for the active-site peptide peak of aged DFP-inhibited BChE, corresponding to a monoisopropylphosphate adduct. Similarly, the analogous mass shift for aged MIP-inhibited BChE was 122.4 +/- 0.7 Da, corresponding to a monoisopropylphosphoroamido adduct. Therefore, we conclude that the MIP-BChE conjugate ages by loss of a single isopropylamine group, in contrast to MIP-inhibited AChE or NEST.
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PMID:Mechanism of aging of mipafox-inhibited butyrylcholinesterase. 1732 78