β-endorphin metabolism by CD4+ and CD8+ T cells, and the thymoma cell line, EL4, was investigated. In all three cell types, extracellular β-endorphin was metabolized exclusively by a secreted, metal-dependent, thiol peptidase. The enzyme activity is expressed constitutively in EL4 cells and following activation of CD4+ and CD8+ T cells with anti-CD3 antibody. The enzyme is not one of the proteinases associated with cytolytic T cells and does not appear to be identical with any previously described β-endorphin metabolizing enzyme. The enzyme cleaves β-endorphin at approximately equal rates at either of two sites to yield β-endorphin1-17 (which is γ-endorphin), β-endorphin1-18, β-endorphin18-31 and β-endorphin19-31. Evidence in the literature indicates that these N- and C-terminal peptides which contain, respectively, the opioid and non-opioid receptor binding domains of β-endorphin, are biologically active. Thus, it is likely that this new T cell peptidase has important immunoregulatory activity.
|Number of pages||11|
|State||Published - Mar 1996|
Bibliographical noteFunding Information:
We would like to thank Carolyn Moomaw and Willa Rollerson of Dr. Clive Slaughter's laboratory at the University of Texas Southwestern Medical Center for performing the peptide microsequencing and amino acid analyses to identify the/3-endorphin metabolites; and Dr. Mike McGuire, also of the University of Texas Southwestern Medical Center, for many helpful discussions. This work was supported in part by U.S. Public Health Service Grant DA07062 (GLC), DA08801 (BCM), and DA02243 (LBH).
- T cell peptidase
- β-Endorphin metabolism
ASJC Scopus subject areas