Phosphorylation biological

Phosphorus-containing macrocycles, 990, 996, 998 macrocychc effect, 1002 ring size, 1003 stereochemistry, 1003 Phosphorus heterocycles transition metal complexes, 1041 Phosphorus ligands, 989-1061 ir-acid series, 1033 bonding, 1030-1041 cone angle concept, 1012 trigonal bipyramidal complexes, 1036 Phosphorus oxychloride metal complexes, 500 Phosphorus ylides transition metal complexes, 1056 Phosphorylation biological, 978 Phosvitin, 975 Photochromism... 

The other property of Mn which has important biochemical consequences is that it is a close, but not exact, surrogate of Mg. As we saw in Chapter 10, Mg is confined to a strict octahedral coordination geometry, with ligand bond angles close to 90°, making it an ideal stmcturaF cation, particularly for phosphorylated biological... 

The biological transformations that involve ATP are both numerous and funda mental They include for example many phosphorylation reactions m which ATP trans fers one of its phosphate units to the —OH of another molecule These phosphoryla tions are catalyzed by enzymes called kinases An example is the first step m the metabolism of glucose... 

The alkyl and alkoxy substituents of phosphate or phosphonate esters also affect the phosphorylating abiUty of the compound through steric and inductive effects. A satisfactory correlation has been developed between the quantitative measure of these effects, Tafts s O, and anticholinesterase activity as well as toxicity (33). Thus long-chain and highly branched alkyl and alkoxy groups attached to phosphoms promote high stabiUty and low biological activity. 

The use of QM-MD as opposed to QM-MM minimization techniques is computationally intensive and thus precluded the use of an ab initio or density functional method for the quantum region. This study was performed with an AMi Hamiltonian, and the first step of the dephosphorylation reaction was studied (see Fig. 4). Because of the important role that phosphorus has in biological systems [62], phosphatase reactions have been studied extensively [63]. From experimental data it is believed that Cys-i2 and Asp-i29 residues are involved in the first step of the dephosphorylation reaction of BPTP [64,65]. Alaliambra et al. [30] included the side chains of the phosphorylated tyrosine, Cys-i2, and Asp-i 29 in the quantum region, with link atoms used at the quantum/classical boundaries. In this study the protein was not truncated and was surrounded with a 24 A radius sphere of water molecules. Stochastic boundary methods were applied [66]. 

FIGURE 10.13 Some of the sequence homologies in the nucleotide binding and phosphorylation domains of Na, K -ATPase, Ca -ATPase, and gastric H, K -ATPase. (Adapted from j0rgensm, P. L., and Andersen, J. R, 1988. Structnral basis for Ei - E2 confoyinational transitions in Na, K -pnmp and Cc -pnmp proteins. Journal of Membrane Biology 103 95-120)... 

Huang, D., Wilson, W. A., and Roach, P. J., 1997. Glucose-6-P control of glycogen syndiase phosphorylation in yeast. Journal of Biological Chemistry 272 22495-22501. 

Yet another difference is that laboratory reactions are often done using relatively small, simple reagents such as Br2, HC1, NaBH4, OO3, and so forth, while biological reactions usually involve relatively complex "reagents" called coenzymes. In the hexokinase-catalyzed phosphorylation of glucose just shown,... 

As an example of two reactions that are coupled, look at the phosphorylation reaction of glucose to yield glucose 6-phosphate plus water, an important step in the breakdown of dietary carbohydrates. The reaction of glucose with HOPO 2- does not occur spontaneously because it is energetically unfavorable, with AG° = + 13.8 kj/mol. (The standard free-energy change for a biological reaction is denoted AG0 and refers to a process in which reactants and products have a concentration of 1.0 M in a soiution with pH = 7.)... 

Pleckstrin homology domain (PH-domain) was first identified at the amino and carboxyl termini of a haematopoietic protein called pleckstrin. PH-domain, a protein region of approximately 120 amino acids, by binding to phosphatidylinositol lipids of the biological membranes induces the translocation of the PH-domain containing protein to membrane compartment. Various PH-domains possess specificities for phosphoinositides phosphorylated at different sites within the inositol ring. 

The biological significance of chitosan biomaterials in the hiunan body depends largely on the actions that certain hydrolases exert on them. The resulting chitoohgomers stimulate various cells, while the released monomers are phosphorylated and incorporated into hyaluronan, keratan sulphate and chondroitin sulphate, components of the intracellular matrix and connective tissue [348]. 

Even if organocatalysis is a common activation process in biological transformations, this concept has only recently been developed for chemical applications. During the last decade, achiral ureas and thioureas have been used in allylation reactions [146], the Bayhs-Hillman reaction [147] and the Claisen rearrangement [148]. Chiral organocatalysis can be achieved with optically active ureas and thioureas for asymmetric C - C bond-forming reactions such as the Strecker reaction (Sect. 5.1), Mannich reactions (Sect. 5.2), phosphorylation reactions (Sect. 5.3), Michael reactions (Sect. 5.4) and Diels-Alder cyclisations (Sect. 5.6). Finally, deprotonated chiral thioureas were used as chiral bases (Sect. 5.7). 

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