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Updated: May 11, 2026
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Single-molecule Super-resolution Imaging of Phosphatidylinositol 4,5-bisphosphate in the Plasma Membrane with Novel Fluorescent Probes
Published on: October 15, 2016
A diphosphoinositide kinase in rat mast cell granules
M Kurosawa1, Y Okayama, S Kobayashi
1Department of Internal Medicine, Gunma University School of Medicine, Maebashi, Japan.
The Journal of Allergy and Clinical Immunology
|July 1, 1989
Summary
Rat mast cell granules contain diphosphoinositide kinase, an enzyme crucial for synthesizing triphosphoinositide using adenosine triphosphate. This enzyme
Area of Science:
- Biochemistry
- Cell Biology
- Enzymology
Background:
- Mast cells are key players in allergic responses.
- Mast cell granules store various bioactive mediators.
- Understanding granule-associated enzymes is vital for cellular function.
Purpose of the Study:
- To identify and characterize diphosphoinositide kinase activity within rat serosal mast cell granules.
- To elucidate the enzymatic properties and localization of this kinase.
Main Methods:
- Isolation of intact granules from purified rat serosal mast cells using Percoll gradient centrifugation.
- Enzymatic assays to measure triphosphoinositide synthesis.
- Kinetic analysis including determination of Km and optimal cofactor concentrations.
- Incubation studies varying time and temperature.
- Comparative phosphorylation assays on intact versus broken membrane granules.
Main Results:
- Diphosphoinositide kinase was identified in mast cell granules, catalyzing triphosphoinositide formation from diphosphoinositide.
- The enzyme requires adenosine triphosphate (ATP) and divalent cations (Mg2+ or Mn2+).
- Kinetic parameters (Km for ATP, optimal Mg2+/Mn2+ concentrations) were determined.
- Synthesis is dependent on incubation time and temperature.
- Inhibitory effects of cyclic adenosine monophosphate (cAMP), adenosine, ADP, and AMP were observed.
- Phosphorylation occurs on the cytoplasmic surface of the granules.
Conclusions:
- Rat mast cell granules possess a diphosphoinositide kinase involved in phosphoinositide metabolism.
- The enzyme's localization to the cytoplasmic surface suggests its role in membrane-associated signaling pathways.
- Further research into this enzyme could reveal new therapeutic targets for mast cell-related disorders.
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