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Related Experiment Videos

Activation and membrane binding of carboxypeptidase E.

L D Fricker1

  • 1Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461.

Journal of Cellular Biochemistry
|December 1, 1988
PubMed
Summary

Carboxypeptidase E (CPE) enzyme activity increases when extracted from membranes. This activation is due to conformational changes, not conversion to an active form, impacting peptide hormone processing.

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Area of Science:

  • Biochemistry
  • Enzymology
  • Cell Biology

Background:

  • Carboxypeptidase E (CPE) is an enzyme involved in processing peptide hormones and neurotransmitters.
  • Both soluble and membrane-associated forms of CPE exist in secretory granules.

Purpose of the Study:

  • To investigate how membrane association affects Carboxypeptidase E activity.
  • To understand the mechanism behind CPE activation upon extraction.

Main Methods:

  • Extraction of bovine pituitary membranes using Triton X-100/NaCl or high pH buffers.
  • Assaying CPE activity using a dansyl-Phe-Ala-Arg substrate.
  • Inhibition studies with bromoacetyl-D-arginine.

Main Results:

  • Extraction with NaCl/Triton X-100 or high pH buffers solubilized membrane-associated CPE and increased its activity 2-3 fold.
  • Extracted CPE exhibited a lower Km for the substrate compared to membrane-associated CPE.
  • NaCl/Triton X-100 treatment increased Vmax, while high pH treatment did not affect Vmax.

Conclusions:

  • Membrane extraction induces conformational changes in CPE, enhancing its catalytic activity.
  • The observed activation is not due to conversion from an inactive to active form.
  • CPE's interaction with membranes influences its enzymatic function in peptide processing.

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