Phosphorus biological function

Preparations are listed in Table 47. Main interest lies in determining how metal ions catalyze the hydrolysis of ADP and ATP. ATP plays a crucial role in the energy metabolism of all living cells and divalent metal ions (Mg +, Mn " and Ca ) play an important role in these phosphoryl transfer processes. Divalent metal ions such as Mg +, Ca, Zn, Cu and Mn " provide only modest in vitro catalysis "" and stronger, more specific coordination to phosphate units appears to be required by the enzyme. Co " (and Cr" ) complexes of ADP and ATP have been shown to mimic many of the biological functions of the Mg" enzyme, and since the cobalt(III)-phosphatc coordination remains intact, the specificity of alternative coordination sites, and the stereochemical requirements at phosphorus, have been elucidated in some cases. Often the Co "-enzyme species is biologically active and several enzymic functions of ATP have been examined in this manner. 

The central role of cyclic nucleotides in regulating a wide range of important biological functions requires examination of the mechanisms of their enzymic synthesis and breakdown. Above all, their biological importance demands a response to the question What design feature of cyclic nucleotides makes these molecules ideal as intracellular messengers In the light of the subject of this review, we must add the rider Is there a role for nucleophilic substitution at phosphorus in protein kinase activation ... 

Because of the possibility of its biosynthesis in the body and its biological function (it is an antirachitic vitamin connected with the metabolism of calcium and phosphorus, which are necessary for growth, development and maintenance of bone structure), some reports state that vitamin Dj is more a hormone than a vitamin. 

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]. 

Mechanisms may be readily envisaged where this reaction may lead to phos-phoryl transfer through nucleophilic attack with ring opening on phosphorus followed by hydrolysis of the acyclic acyl phosphate. In biological systems this may function as an alternative to the metaphosphate reaction. 

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