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Kinetics of irreversible activation of adenylate cyclase of fat cell membranes by phosphonium and phosphoramidate analogs of gtp1.

Publication ,  Journal Article
Jacobs, S; Bennett, V; Cuatrecasas, P
Published in: J Cyclic Nucleotide Res
July 1976

The ability of guanylylimidodiphosphate (GMP=P(NH)P) and guanylylmethylenediphosphonate (GMP-P(CH2)P) to activate adenylate cyclase activity has been studied by incubating these analogs with fat cell membranes followed by thorough washing of the membranes before assay of enzyme activity. GMP-P(NH)P is hydrolyzed by membrane preparations from several tissues. A pyruvate kinase regenerating system maintains the concentration of GMP-P(NH)P and thereby augments the ability of suboptimal concentrations of GMP-P(NH)P to activate adenylate cyclase. GTP inhibits activation of fat cell membrane adenylate cyclase by GMP-P(NH)P but this inhibition is overcome by time. This is consistent with the virtually irreversible nature of the GMP-P(NH)P activation, and with the inability of GTP to reverse the stimulated state of the enzyme. Although the initial rate of enzyme activation is highly dependent on the concentration of GMP-P(NH)P, with increasing times of incubation nearly the same maximal extent of activation is seen over a wide range of concentrations. Thus, it is not possible to estimate true affinity constants (at equilibrium) for GMP-P(NH)P, as anticipated from the virtually irreversible character of the activation process.

Duke Scholars

Published In

J Cyclic Nucleotide Res

ISSN

0095-1544

Publication Date

July 1976

Volume

2

Issue

4

Start / End Page

205 / 223

Location

United States

Related Subject Headings

  • Turkeys
  • Rats
  • Organophosphonates
  • Magnesium
  • Kinetics
  • Isoproterenol
  • Guanosine Triphosphate
  • Erythrocytes
  • Enzyme Activation
  • Cell Membrane
 

Citation

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Jacobs, S., Bennett, V., & Cuatrecasas, P. (1976). Kinetics of irreversible activation of adenylate cyclase of fat cell membranes by phosphonium and phosphoramidate analogs of gtp1. J Cyclic Nucleotide Res, 2(4), 205–223.
Jacobs, S., V. Bennett, and P. Cuatrecasas. “Kinetics of irreversible activation of adenylate cyclase of fat cell membranes by phosphonium and phosphoramidate analogs of gtp1.J Cyclic Nucleotide Res 2, no. 4 (July 1976): 205–23.
Jacobs, S., et al. “Kinetics of irreversible activation of adenylate cyclase of fat cell membranes by phosphonium and phosphoramidate analogs of gtp1.J Cyclic Nucleotide Res, vol. 2, no. 4, July 1976, pp. 205–23.

Published In

J Cyclic Nucleotide Res

ISSN

0095-1544

Publication Date

July 1976

Volume

2

Issue

4

Start / End Page

205 / 223

Location

United States

Related Subject Headings

  • Turkeys
  • Rats
  • Organophosphonates
  • Magnesium
  • Kinetics
  • Isoproterenol
  • Guanosine Triphosphate
  • Erythrocytes
  • Enzyme Activation
  • Cell Membrane