Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01189 (beta-endorphin)
 21,003 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Magnesium is required for over 300 enzyme systems and is critical for many cellular functions including oxidative phosphorylation, glycolysis, DNA transcription and protein synthesis. Studies suggest that the modern Western diet and lifestyle may lead to magnesium deficiency, and this appears to be associated with a wide range of medical conditions. Magnesium deficiency decreases seizure thresholds in animal models of epilepsy and indeed low magnesium concentration in the perfusate is a common method of generating spontaneous epileptiform discharges from rat hippocampal slices. Magnesium is a potential modulator of seizure activity because of its ability to antagonize excitation through the N-methyl-d-aspartate receptor. Some studies have shown that people with epilepsy have lower magnesium levels than people without epilepsy. There are case reports of seizures being controlled with magnesium supplementation in people with specific conditions, and recently in an open randomized trial, children with infantile spasms responded better to adrenocorticotropic hormone (ACTH) plus magnesium than to ACTH alone. We hypothesise that magnesium supplementation can reduce seizures in people with epilepsy. This hypothesis can be tested in a controlled randomised supplementation trial. If proven, magnesium supplementation needs to be considered in the overall management of people with refractory epilepsy.
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PMID:Can magnesium supplementation reduce seizures in people with epilepsy? A hypothesis. 2254 96

The hydrolysis mechanisms of phosphor-monoester monoanions NPP(-) (p-nitrophenyl phosphate) catalyzed by unsymmetrical bivalent dinuclear complexes are explored using DFT calculations in this report. Four basic catalyst-substrate binding modes are proposed, and two optional compartments for the location of the nucleophile-coordinated metal center are also considered. Five plausible mechanisms are examined in this computational study. Mechanisms 1, 2, and 3 employ an unsymmetrical dizinc complex. All three mechanisms are based on concerted SN2 addition-substitution pathways. Mechanism 1, which involves more electronegative oxygen atoms attached to the imine nitrogen atoms in the nucleophile-coordinated compartment, was found to be more competitive compared to the other two mechanisms. Mechanisms 4 and 5 are based on consideration of the substitution of the bivalent metal centers and the intrinsic flexibility of the ligand. Both mechanisms 4 and 5 are based on stepwise SN2-type reactions. Magnesium ions with hard base properties and more available coordination sites were found to be good candidates as a substitute in the M(II) dinuclear phosphatases. The reaction energy barriers for the more distorted complexes are lower than those of the less distorted complexes. The proper intermediate distance and a functional second coordination sphere lead to significant catalytic power in the reactions studied. More importantly, the mechanistic differences between the concerted and the stepwise pathways suggest that a better nucleophile with more available coordination sites (from either the metal centers or a functional second coordination sphere) favors concerted mechanisms for the reactions of interest. The results reported in the paper are consistent with and provide a reasonable interpretation for experimental observations in the literature. More importantly, our present results provide some practical suggestions for the selection of the metal centers and how to approach the design of a catalyst.
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PMID:Mechanismic investigation on the cleavage of phosphate monoester catalyzed by unsymmetrical macrocyclic dinuclear complexes: the selection of metal centers and the intrinsic flexibility of the ligand. 2464 77


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