Inhibition by glutamate of phosphate-dependent glutaminase of rat kidney

Shapiro, Richard A.; Morehouse, R F; Curthoys, Norman P.

doi:10.1042/bj2070561

Cited by 53 publications

(26 citation statements)

References 21 publications

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“…It was found it to be sigmoidal for rat kidney (Shapiro et al, 1982) and brain Mb-PAG, and in our hands it was sigmoidal also both for pig and rat Sol-PAG Roberg et al, 2000). Mb-PAG from brain and kidney has a lower apparent K a value for P i than Sol-PAG.…”

Section: Membrane-associated and Soluble Fractions Of Pag As Comparedmentioning

confidence: 60%

Kinetics and localization of brain phosphate activated glutaminase

Kvamme

Torgner

Roberg

2001

J of Neuroscience Research

110

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The cellular concentration of phosphate, the main activator of phosphate activated glutaminase (PAG) is rather constant in brain and kidney. The enzyme activity, however, is modulated by a variety of compounds affecting the binding of phosphate, such as glutamate, calcium, certain long chain fatty acids, fatty acyl CoA derivatives, members of the tricarboxylic acid cycle and protons (Kvamme et al. [2000] Neurochem. Res. 25:1407-1419). Therefore, the kinetic and allosteric properties of the enzyme are essential for regulating the enzyme activity in situ, especially because the enzymically active pool of PAG is assumed to have an external localization in the inner mitochondrial membrane, being exposed to cytosolic variation in the content of effectors. This has largely been overlooked. A hypothetical model for the allosteric interactions based on the sequential induced fit allosteric model by Koshland et al. ([1966] Biochemistry 5:365-385) is presented. Furthermore, it has been generally accepted that there exist only two isoforms of PAG, the kidney PAG that is similar to brain PAG, and the liver PAG. Therefore, the immunoreactivity of brain cells against kidney PAG antibodies has been considered a measure of PAG protein. Gomez-Fabre et al. ([2000] Biochem. J. 345:365-375) recently found, however, that a PAG mRNA from human breast cancer ZR75 cells is present in human brain and liver, but not in the kidney. We observed only traces of PAG immunoreactivity in cultured astrocytes and cultured neuroblastoma cells, regardless whether antibodies against the C- and N-termini of kidney PAG or antibodies against liver PAG were used, but considerable enzyme activity, demonstrating hitherto unknown isoforms of PAG (Torgner et al. [2001] FEBS Lett. 268(Suppl 1):PS2-031).

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Section: Membrane-associated and Soluble Fractions Of Pag As Comparedmentioning

confidence: 60%

Kinetics and localization of brain phosphate activated glutaminase

Kvamme

Torgner

Roberg

2001

J of Neuroscience Research

110

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“…4A) conditions, respectively. GLNase activity was not inhibited by the Glu that accumulated during the assay because the amount was orders below the inhibition concentration of the enzyme (Shapiro et al, 1982). Compounds in the extract did not seem to inhibit the cycling reaction significantly.…”

Section: Confirmation With Cell Extractmentioning

confidence: 96%

Measurement of key metabolic enzyme activities in mammalian cells using rapid and sensitive microplate‐based assays

Janke

Genzel

Wahl

et al. 2010

Biotech & Bioengineering

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Sensitive microplate-based assays to determine low levels of key enzyme activities in mammalian cells are presented. The enzyme platform consists of four cycling assays to measure the activity of 28 enzymes involved in central carbon and glutamine metabolism. The sensitivity limit of all cycling assays was between 0.025 and 0.4 nmol product. For the detection of glutaminase activity, a new glutamate cycle system involving the enzymes glutamate dehydrogenase and aspartate transaminase was established. The relative standard deviation of the method was found to be 1.7% with a limit of detection of 8.2 pmol and a limit of quantitation of 24.8 pmol. Hence, cell extracts could be highly diluted to reduce interferences caused by other components in the extract, which in addition minimized underestimates or overestimates of actual enzyme activities. Since substrate concentrations could be maintained at a nearly constant level throughout the assay product accumulation during the reaction was low, which minimized product inhibition. As an example, the enzyme platform was used to investigate maximum enzyme activities of stationary-phase MDCK cells grown in serum-containing GMEM medium as typically used in influenza vaccine production.

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“…This last observation may explain the high tumor glutaminase activity found in tumors compared with non-neoplastic tissue (Table 2). For rat kidney and tumor glutaminase, increasing the phosphate concentration from 5 to 100 mM Pi augments the glutamine affinity and the km for glutamine diminishes from 36 to 4 mM (Shapiro et al, 1982).…”

Section: Glutaminasementioning

confidence: 98%

Bioenergetic pathways in tumor mitochondria as targets for cancer therapy and the importance of the ROS-induced apoptotic trigger

Ralph

Rodrı́guez-Enrı́quez

Neužil

et al. 2010

Molecular Aspects of Medicine

143

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Mitochondria are emerging as idealized targets for anti-cancer drugs. One reason for this is that although these organelles are inherent to all cells, drugs are being developed that selectively target the mitochondria of malignant cells without adversely affecting those of normal cells. Such anti-cancer drugs destabilize cancer cell mitochondria and these compounds are referred to as mitocans, classified into several groups according to their mode of action and the location or nature of their specific drug targets. Many mitocans selectively interfere with the bioenergetic functions of cancer cell mitochondria, causing major disruptions often associated with ensuing overloads in ROS production leading to the induction of the intrinsic apoptotic pathway. This in-depth review describes the bases for the bioenergetic differences found between normal and cancer cell mitochondria, focussing on those essential changes occurring during malignancy that clinically may provide the most effective targets for mitocan development. A common theme emerging is that mitochondrially mediated ROS activation as a trigger for apoptosis offers a powerful basis for cancer therapy. Continued research in this area is likely to identify increasing numbers of novel agents that should prove highly effective against a variety of cancers with preferential toxicity towards malignant tissue, circumventing tumor resistance to the other more established therapeutic anti-cancer approaches.

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Inhibition by glutamate of phosphate-dependent glutaminase of rat kidney

Cited by 53 publications

References 21 publications

Kinetics and localization of brain phosphate activated glutaminase

Kinetics and localization of brain phosphate activated glutaminase

Measurement of key metabolic enzyme activities in mammalian cells using rapid and sensitive microplate‐based assays

Bioenergetic pathways in tumor mitochondria as targets for cancer therapy and the importance of the ROS-induced apoptotic trigger

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