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Updated: Aug 8, 2026

NMR-Based Activity Assays for Determining Compound Inhibition, IC50 Values, Artifactual Activity, and Whole-Cell Activity of Nucleoside Ribohydrolases
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NMR-Based Activity Assays for Determining Compound Inhibition, IC50 Values, Artifactual Activity, and Whole-Cell Activity of Nucleoside Ribohydrolases

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Effect of nucleoside 5'-di- and 5'-tri-phosphates on pancreatic ribonuclease activity

W Gamble1, L D Wright

  • 1Graduate School of Nutrition, Cornell University, Ithaca, N.Y., and Department of Chemistry and Science Research Institute, Oregon State University, Corvallis, Oregon, U.S.A.

The Biochemical Journal
|November 1, 1965
PubMed

Insights

Adenosine diphosphate (ADP) and other purine nucleoside phosphates inhibit ribonuclease activity by binding to the enzyme-substrate complex. This uncompetitive inhibition highlights the essential role of the polyphosphate group for enzyme inhibition.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Enzymology

Background:

  • Ribonucleases (RNases) are enzymes crucial for RNA metabolism.
  • Understanding the regulation of RNase activity is vital for controlling cellular processes.
  • Nucleoside phosphates are known modulators of enzyme function.

Purpose of the Study:

  • To investigate the inhibitory effects of various nucleoside diphosphates on ribonuclease activity.
  • To elucidate the mechanism of inhibition by adenosine diphosphate (ADP).
  • To determine the structural requirements for effective inhibition of ribonuclease.

Main Methods:

  • Enzyme assays measuring phosphotransferase activity of ribonuclease.
  • Testing inhibition by various purine and pyrimidine nucleoside diphosphates.
  • Kinetic analysis to determine the type of inhibition (uncompetitive).

Main Results:

  • Adenosine diphosphate (ADP), adenosine triphosphate (ATP), and guanosine diphosphate (GDP) significantly inhibited ribonuclease.
  • Pyrimidine nucleoside diphosphates (CDP, UDP) showed no significant inhibition.
  • ADP exhibited uncompetitive inhibition, suggesting interaction with the enzyme-substrate complex.
  • The polyphosphate moiety of purine nucleoside diphosphates was essential for optimal inhibition.

Conclusions:

  • Purine nucleoside diphosphates, particularly ADP, are potent inhibitors of ribonuclease phosphotransferase activity.
  • Inhibition is uncompetitive, indicating the inhibitor binds to the enzyme-substrate complex.
  • The polyphosphate chain is critical for the inhibitory action, suggesting a specific binding interaction.

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