Polyphosphates, synthesis with

The products of the PI3-kinase reaction are different phosphoinositide derivatives phosphorylated at the 3 position, of which PtdIns(3,4,5)P3 has the greatest regulatory importance. PtIns(3,4,5)P3, like cAMP, has the function of a messenger substance that activates effector molecules in the sequence for further signal conduction. In contrast to cAMP, PtdIns(3,4,5)P3 is localized in the cell membrane and performs its function in close association with processes at the cell membrane. The concentration of PtdIns(3,4,5)P3 in the cell depends both on the rates of synthesis by PI3-kinases and the rates of hydrolysis of its phosphate residues. Several inositol polyphosphate phosphatases have been identified that remove the phosphates at position 3 or 5 of the inositol moiety. Among the inositol polyphosphate phosphatases with specificity for the 3-position, the PTEN phosphatase has been identified as a tumor supressor protein (see below). 

Klosinski, P., Penczek, S. Teichoic Acids and Their Models Membrane Biopolymers with Polyphosphate Backbones. Synthesis, Structure and Properties. Vol. 79, pp. 139-157. 

Similar changes in the absorption spectrum were observed for colloidal ZnS. A colloid in methanol solution at —77 °C had a maximum at 228 nm. Upon aging, this maximum became weaker and a new one arose at 243 nm. Further aging at room temperature led to a spectrum with one maximum at 265 nm. It was concluded that the —77 °C synthesis created two very small types of crystallites (<2 nm) identified by the 228 and 243 nm peaks. Upon warming, those crystallites were lost and new crystallites of about 2 nm were formed which persisted at room temperature Absorption spectra with several maxima were also observed for ZnSe, CdSe and In Soj stabilized by polyphosphate... 

Miihlradt, P.R Synthesis of high molecular weight polyphosphate with a partially purified enzyme from Salmonella. J. Gen. Microbiol., 68, 115-122 (1971)... 

Membrane Biopolymers with Polyphosphate Backbones Synthesis, Structure and Properties... 

The accumulation of PolyPs in cells results from two processes synthesis and utilization of PolyP. The dynamics of the known PolyP-synthesizing enzymes, i.e. polyphosphate kinase and 1,3-diphosphoglycerol-polyphosphate phosphotransferase, showed that these enzyme activities weakly correlate with the dynamics of PolyP accumulation under standard growth conditions (see Figure 8.1). The main peak of polyphosphate kinase activity was... 

After ppkl inactivation, the knockout mutants show no growth defects when compared with the parent strain. One of the remarkable defects in these mutants was the loss of motility (Rashid and Kornberg, 2000 Rashid et al, 2000a,b). A low-residual polyphosphate kinase activity was detected in these mutants (Zago et al., 1999) and attributed to the activity of the ppkl gene (Zhang et al., 2002). However, one cannot exclude the existence of other pathways of PolyP synthesis in this bacterium. 

Some authors doubt the possibility of a direct interrelation between PolyP and photosynthesis in algae (Rubtsov et al, 1977 Rubtsov and Kulaev, 1977). The following facts support this point of view. No high-molecular-weight PolyP was found in the chloroplasts of Acetabularia mediterranea (Rubtsov et al, 1977). The inhibitor analysis and detection of polyphosphate kinase activity in this alga (Rubtsov and Kulaev, 1977) point to the fact that PolyP is not directly, but rather indirectly, connected with the photosynthesis through the formation of ATP, which provides energy for P transport and PolyP synthesis. 

Polyphosphate kinase has been found able to phosphorylate nucleoside diphosphates to give nucleoside triphosphates, using PolyP as a phosphate donor. Therefore, the possibility of using PolyP and polyphosphate kinase instead of phosphoenol pyruvate and pyruvate kinase for enzymatic oligosaccharide synthesis was examined, because PolyP is quite cheap when compared with phosphoenol pyruvate (Noguchi and Shiba, 1998 Shiba et al, 2000). Attempts were made to synthesize N-acetyllactosamine (Gal (f> 1-4) GlcNAc) using the nucleoside diphosphate kinase-like activity of polyphosphate kinase, where UDP-Glc pyrophosphorylase and UDP-Glc 4-epimerase catalyse the synthesis of UDP-Glc from... 

G. Schramm, G. Lazmann and F. Bechman (1967). Synthesis of a- and /8-Adenosine and of a- and /S-2-deoxyadenosine with phenyl polyphosphate. Biochim. Biophys. Acta, 145, 221-230. 

---