@phdthesis{Riewe2008,
  author    = {Riewe, David},
  title     = {The relevance of adenylate levels and adenylate converting enzymes on metabolism and development of potato (Solanum tuberosum L.) tubers},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27323},
  school      = {Universit{\"a}t Potsdam},
  year      = {2008},
  abstract  = {Adenylates are metabolites with essential function in metabolism and signaling in all living organisms. As Cofactors, they enable thermodynamically unfavorable reactions to be catalyzed enzymatically within cells. Outside the cell, adenylates are involved in signalling processes in animals and emerging evidence suggests similar signaling mechanisms in the plants' apoplast. Presumably, apoplastic apyrases are involved in this signaling by hydrolyzing the signal mediating molecules ATP and ADP to AMP. This PhD thesis focused on the role of adenylates on metabolism and development of potato (Solanum tuberosum) by using reverse genetics and biochemical approaches. To study the short and long term effect of cellular ATP and the adenylate energy charge on potato tuber metabolism, an apyrase from Escherichia coli targeted into the amyloplast was expressed inducibly and constitutively. Both approaches led to the identification of adaptations to reduced ATP/energy charge levels on the molecular and developmental level. These comprised a reduction of metabolites and pathway fluxes that require significant amounts of ATP, like amino acid or starch synthesis, and an activation of processes that produce ATP, like respiration and an immense increase in the surface-to-volume ratio. To identify extracellular enzymes involved in adenylate conversion, green fluorescent protein and activity localization studies in potato tissue were carried out. It was found that extracellular ATP is imported into the cell by an apoplastic enzyme complement consisting of apyrase, unspecific phosphatase, adenosine nucleosidase and an adenine transport system. By changing the expression of a potato specific apyrase via transgenic approaches, it was found that this enzyme has strong impact on plant and particular tuber development in potato. Whereas metabolite levels were hardly altered, transcript profiling of tubers with reduced apyrase activity revealed a significant upregulation of genes coding for extensins, which are associated with polar growth. The results are discussed in context of adaptive responses of plants to changes in the adenylate levels and the proposed role of apyrase in apoplastic purinergic signaling and ATP salvaging. In summary, this thesis provides insight into adenylate regulated processes within and outside non-photosynthetic plant cells.},
  language  = {en}
}
@article{YarmanSchulzSygmundetal.2014,
  author    = {Yarman, Aysu and Schulz, Christopher and Sygmund, Cristoph and Ludwig, Roland and Gorton, Lo and Wollenberger, Ursula and Scheller, Frieder W.},
  title     = {Third generation ATP sensor with enzymatic analyte recycling},
  series = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis},
  volume    = {26},
  journal   = {Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis},
  number    = {9},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1040-0397},
  doi       = {10.1002/elan.201400231},
  pages     = {2043 -- 2048},
  year      = {2014},
  abstract  = {For the first time the direct electron transfer of an enzyme - cellobiose dehydrogenase, CDH - has been coupled with the hexokinase catalyzed competition for glucose in a sensor for ATP. To enhance the signal output for ATP, pyruvate kinase was coimmobilized to recycle ADP by the phosphoenolpyruvate driven reaction. The new sensor overcomes the limit of 1:1 stoichiometry of the sequential or competitive conversion of ATP by effective enzymatic recycling of the analyte. The anodic oxidation of the glucose converting CDH proceeds at electrode potentials below 0 mV vs. Ag vertical bar AgCl thus potentially interfering substances like ascorbic acid or catecholamines do not influence the measuring signal. The combination of direct electron transfer of CDH with the enzymatic recycling results in an interference-free and oxygen-independent measurement of ATP in the lower mu molar concentration range with a lower limit of detection of 63.3 nM (S/N=3).},
  language  = {en}
}