Magnesium ions activation

The observation that calcium and magnesium ion activity coefficients are generally similar in aqueous solution has led to the concept that the calcium to magnesium ion concentration ratio should be fixed at a given temperature and... 

Henderson, A. R., The effect of feeding with a tryptophan-free amino acid mixture on rat liver magnesium ion-activated deoxyribonucleic acid-dependent ribonucleic acid polymerase, Biochem. ]., 120[1], 205, 1970. 

Figure 2, Magnesium ion activity in solution vs. pH value for freshly prepared solutions of MgCU. The pH values were adjusted by NaOH and sodium silicate solutions with the indicated ratios of Si02 Na20, Key , NaOH +, 0.5 A, 2.0 ...

Figure 5. Reduction in magnesium ion activity vs, silica concentration for sodium silicate solutions with SiOt NasQ ratio values of 0.5 f+J, 2.0 f and 3,8 (O), The pH values are shown in parentheses.

ATP is activated by coordination to magnesium ion, and nucleophilic addition of a fatty acid caiboxylate to phosphorus then yields a pentacoordinate intermediate. . ... 

Dukhovich, A. F., Ugarova, N. N., Berezin, I. V., and Filippova, N. Y. (1986). Role of magnesium ions in the regulation of catalytic activity of the firefly luciferase. Dokl. Akad. Nauk SSSR 288 1500-1504. 

It is possible to separate a soap-LSDA dispersion by ultrafiltration through a polymeric membrane [33]. The filtrate contained sodium and some magnesium ions but no calcium soaps or LSDA. The separated substances on the membrane could be readily dispersed in water in which they retained a high degree of surface activity. 

Trentham, D.R., Bardsley, R.G., Eccleston, J.F., Weeds, G. (1972). Elementary processes of the magnesium ion-dependent adenosine triphosphatase activity of heavy meromyosin. Biochem. J. 126, 635-644. 

The GMT in human serum reacts most rapidly with Y-glutamyl-p-nitroanilide at pH 8.2. The same activity is found in 2-amino-2-methylpropane-l 3 diol, diethanolamine, triethanolamine and tris buffers. Magnesium ions have no effect on the activity but favor the solubilization of the substrate. Bondar and Moss (54) found that free glutamate, due to elevated serum glutamate concentrations or glutamate released by substrate breakdown, increases the apparent GMT activity. They concluded that the assay should be performed in the presence of 1.0 vM/1 glutamate in order to reduce the possibility of falsely elevated results. This was not observed by others. Rowe and co-workers have indicated that certain batches of p-nitroanilide substrate contain impurities which may reduce GMT activity and increase the values ( ). Huesby and Stromme (56) confirmed the presence of such impurities and recommended pyridine extraction for substrate purification. 

Bates et al. reported the construction and characterization of a gold nanoparticle wire assembled using Mg -dependent RNA-RNA interactions for the future assembly of practical nanocircuits [31]. They used magnesium ion-mediated RNA-RNA loop-receptor interactions, in conjunction with 15 nm or 30 nm gold nanoclusters derivatized with DNA to prepare self-assembled nanowires. A wire was deposited between lithographically fabricated nanoelectrodes and exhibited non-linear activated conduction by electron hopping at 150-300 K (Figure 16). 

This must reflect activation of the carbonyl group by magnesium ion, since ketones are less reactive to pure dialkylzinc reagents and tend to react by reduction rather than addition.141 The addition of alkylzinc reagents is also promoted by trimethylsilyl chloride, which leads to isolation of silyl ethers of the alcohol products.142... 

These enzymes catalyse the non-hydrolytic cleavage of bonds in a substrate to remove specific functional groups. Examples include decarboxylases, which remove carboxylic acid groups as carbon dioxide, dehydrases, which remove water, and aldolases. The decarboxylation of pyruvic acid (10.60) to form acetaldehyde (10.61) takes place in the presence of pyruvic decarboxylase (Scheme 10.13), which requires the presence of thiamine pyrophosphate and magnesium ions for activity. 

The use of alkali and alkaline earth group metal ions, especially those of sodium, potassium, magnesium, and calcium, for maintenance of electrolyte balance and for signaling and promotion of enzyme activity and protein function are not discussed in this text. Many of these ions, used for signaling purposes in the exciting area of neuroscience, are of great interest. In ribozymes, RNAs with catalytic activity, solvated magnesium ions stabilize complex secondary and tertiary molecular structure. Telomeres, sequences of DNA at the ends of chromosomes that are implicated in cell death or immortalization, require potassium ions for structural stabilization. 

Farnesyltransferase is a heterodimeric protein composed of an a- and a /1-sub-unit, and zinc and magnesium ions are required for its activity [7,8]. A closely related heterodimeric enzyme is geranylgeranyltransferase I (GGTase I). It also recognizes proteins with a CAAX-box when X is leucine. Both enzymes share the same a-subunit and the requirement for Zn2+ and Mg2+ but the /1-subunits are different. The similarity of these enzymes highlights the importance of selectivity of farnesyltransferase (FT)-inhibitors. 

While having three metal ions in an enzyme active site is uncommon, it is not unique to PLCBc. The well-known alkaline phosphatase from E. coli (APase) contains two zinc ions and a magnesium ion [67], whereas the a-toxin from Clostridiumperfringens [68]. and the PI nuclease from Penicillium citrinum [69] each contain three zinc ions. Indeed, the zinc ions and coordinating ligands of PI nuclease bear an uncanny resemblance to those of PLCBc as the only differ-... 

Larsen, T.M., Wedeking, J.E., Rayment, I. and Reed, G.H. (1996) A carboxylate oxygen of the substrate bridges the magnesium ions at the active site of enolase structure of the yeast enzyme complexed with the equilibrium mixture of 2-phosphoglycerate and phosphoenolpyruvate at 1.8 A resolution, Biochemistry, 30, 4349-4358. 

The enzyme is activated by magnesium ions, has an optimum pH of about 7.5 and offers a very sensitive assay method for ATP but has much wider applications when used in coupled assays with ATP-converting enzymes. 

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