Identification of γ-endorphin-generating enzyme as insulin-degrading enzyme

Afshin Safavi, Bonnie C. Miller, Larry Cottam, Louis B. Hersh

Research output: Contribution to journalArticlepeer-review

74 Scopus citations


The EL-4 thymoma cell line contains a peptidase which converts β- endorphin to β-endorphin 1-17 (γ-endorphin), β-endorphin 1-18, and their corresponding C-terminal fragments. This enzyme was purified approximately 700-fold to a single band on an SDS-polyacrylamide gel (106 kDa) in 16% yield. Estimation of the native molecular weight by molecular sieve chromatography gave a value of ~220 kDa, indicating that this enzyme is a dimer. Peptide sequencing demonstrated this activity can be attributed to insulin degrading enzyme, a previously described member of the inverzincin family (Hooper, 1994). Kinetic studies with a number of peptide substrates indicate that the enzyme preferentially cleaves on the amino side of hydrophobic or basic residues. However, the substrate specificity is more complex since not all basic and hydrophobic residues in a peptide are cleaved. The enzyme exhibits a requirement for a P' 2 residue. On the basis of k(cat)/K(m) values, insulin, growth hormone releasing factor, and β- endorphin are nearly equivalent substrates for the enzyme; however, growth hormone releasing factor and β-endorphin exhibit a 40-fold higher k(cat), but a 10-fold decreased affinity relative to insulin. A role for insulin- degrading enzyme us both a β-endorphin-processing and -inactivating enzyme is implicated from these studies.

Original languageEnglish
Pages (from-to)14318-14325
Number of pages8
Issue number45
StatePublished - 1996

ASJC Scopus subject areas

  • Biochemistry


Dive into the research topics of 'Identification of γ-endorphin-generating enzyme as insulin-degrading enzyme'. Together they form a unique fingerprint.

Cite this