Transphosphorylation, types

Transphosphorylations between Nucleotides Occur in All Cell Types... 

Certain dipositive metal ions not only accelerate the hydrolysis of ATP, as mentioned above, but also assist in the transfer of a phosphoryl group from one molecule to another. Such a nonenzymatic transphosphorylation takes place between ATP and an orthophosphate ion or its monoester in the presence of calcium(II), cadmium(II), and manganese(II). This type of nonenzymatic process can serve as a model for the biologically important enzymatic transphosphorylations that involve ATP, although... 

ATP formation on creatine and MgCl2 concentrations was also examined and the results are summarized in Fig. 6 and Fig. 7. Without creatine, ATP formation occurred later and more slowly but at the same high conversion level. The addition of excess creatine caused acceleration of ATP formation. Without creatine, the induction period took two times longer. As shown in the time conversion curve with heptakis-(2,6-dimethyl)-g-CD (DM-g-CD) without creatine, ATP formation occurred later and more slowly at the same conversion level. Besides these examinations, the effect of O2, buffer solution and temperature were observed. Without O2, the reaction did not proceed. Ionic strength and pH of the phosphate buffer and reaction temperature were optimum under the present conditions. The results obtained here showed the same kind of catalytic activity of the CD in the equilibrium between ADP and ATP in this scheme 1. This new type of transphosphorylation seems to be a... 

In addition to the transphosphorylation reactions discussed in Chapter 4, there are several general types of carbon and nitrogen transfer reactions which also occur in purine and pyrimidine nucleotide biosynthesis and interconversion. Among these are one-carbon and phosphoribosyl transfer reactions, amino group transfer from glutamine and aspartate, and amide syntheses. In most of these processes carbon-nitrogen bonds... 

The arabinose isomerase has been separated from the transphosphoryl-ase specific for ribulose from extracts of E. coli. It had been observed earlier that the product of n-arabinose metabolism in these extracts was an acid-stable pentose phosphate. Thus the product of ribulose phosphorylation was either itself a 5-phosphate or was converted to a moiety of this type such as ribose-5-phosphate. It may be noted that straight-chain sugar phosphates such as ribulose-5-phosphate or 2-desoxy deriva-tives are not as stable to acid as a compound like the furanose ribose-6-phosphate, which may have been the final product analyzed in the study of n-arabinose metabolism. 

The vast majority of the stereochemical studies that have been performed to date are those of enzymes that utilize a nucleotide as a substrate. However, Bruzik and Tsai reported the synthesis of the diastereomers of phosphatidylethanolamine that are chiral by virtue of substitution with 0 and 0 (Bruzik and Tsai, 1982). Their route to the desired product involves the acid-catalyzed hydrolysis of a five-membered ring cyclic phosphoiami-date, which directly yields the ethanolamine moiety on P—N bond cleavage the steps in the synthesis are shown in Fig. 5. dearly, this synthetic strategy is relatively inflexible as to the types of phospholipids that are directly accessible, but the known abihty of phospholipase D to catalyze a facile transphosphorylation reaction (with retention of configuration) does increase the number of chiral phospholipids that can be synthesized. 

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