Subsystem: Phosphate metabolism
This subsystem's description is:
This SS combines different roles, not necessary belonging to one pathway, but related to Phosphorus metabolism. Overview of SS's main functions:
Inorganic polyP is a ubiquitous molecule formed by phosphate (Pi) residues linked by high energy phosphoanhydride bond. PolyP synthesis is catalyzed by a polyphosphate kinase in prokaryotes. PolyP hydrolysis is catalyzed by exo-, endo-polyphosphatases and pyrophosphatases.
(For more details also see:http://www.jbc.org/cgi/content/full/281/3/1516)
Differential regulation of soluble and membrane-bound inorganic pyrophosphatases in the photosynthetic bacterium Rhodospirillum rubrum provides insights into pyrophosphate-based stress bioenergetics: http://jb.asm.org/cgi/content/full/186/16/5418?view=long&pmid=15292143
Three-dimensional structures of mutant forms of E. coli inorganic pyrophosphatase with Asp-->Asn single substitution in positions 42, 65, 70, and 97.:1: (Biochemistry (Mosc). 1998 Jun;63(6):671-84).
Polyphosphate kinase (PPK) catalyzes the reversible transfer of the terminal phosphate of ATP to form a long-chain polyphosphate (polyP).
(References: (http://www.jbc.org/cgi/reprint/267/31/22556?ijkey=a31a41bd99fd23545d01cc668b32dfcd3452070e ;Ahn, K., and Kornberg, A. (1990) J. Biol. Chem. 265, 11734-11739).
Pentose phosphate pathway and isocitrate dehydrogenase are generally considered to be the major sources of the anabolic reductant NADPH. As one of very few microbes, Escherichia coli contains two transhydrogenase isoforms with unknown physiological function that could potentially transfer electrons directly from NADH to NADP+ and vice versa.Proton-translocating transhydrogenase PntAB is a major source of NADPH in E. coli. During standard aerobic batch growth on glucose, 35-45% of the NADPH that is required for biosynthesis is produced via PntAB, whereas pentose phosphate pathway and isocitrate dehydrogenase contribute 35-45% and 20-25%, respectively. The energy-independent transhydrogenase UdhA (TH2in our this subsystem), in contrast, is essential for growth under metabolic conditions with excess NADPH formation, i.e. growth on acetate or in a phosphoglucose isomerase mutant that catabolized glucose through the pentose phosphate pathway. Thus, both isoforms have divergent physiological functions: energy-dependent reduction of NADP+ with NADH by PntAB and reoxidation of NADPH by UdhA. UdhA is not as common as PntAB ortologs. (For more details see: http://www.jbc.org/cgi/content/full/279/8/6613)
The Pho regulon integrates the sensing of environmental inorganic phosphate (Pi) availability with coregulation of gene expression, mediating an adaptive response to Pi limitation. Many aspects of the Pho regulon have been addressed in studies of Escherichia coli; however, it is unclear how transferable this knowledge is to other bacterial systems.
(For more details see:
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