Identification of the cleavage sites of transforming growth factor alpha by insulin-degrading enzymes.
Insulin-degrading enzyme (IDE) is a sulfhydryl-dependent metalloproteinase with a zinc binding site unique to a new class of proteinases. The enzyme is relatively specific for a number of hormones/growth factors, such as insulin, atrial natriuretic peptide, IGF-II, and proinsulin. In this study we have identified the amino-acid bonds cleaved by IDE in transforming growth factor-alpha. High-performance liquid chromatography was used to separate the peptides generated by the degradation of 125I-TGF-alpha. The peptides were then submitted to sequential Edman degradation to determine the peptide bond broken. Cleavage sites were found at amino acids, 10-11 (Asp-Ser), 25-26 (Val-Gln), 28-29 (Asp-Lys), and 30-31 (Pro-Ala). In agreement with studies of cleavage sites of other hormones by this enzyme, no clear amino-acid specificity was seen. However, examination of the sites on a three-dimensional model of TGF-alpha suggest the primary mechanism used by IDE for determining cleavage sites is the tertiary structure of the substrate.
Hamel
F G
FG
University of Nebraska Medical Center, Veteran's Affairs Medical Center, Omaha 68198-3020, USA.
Gehm
B D
BD
Rosner
M R
MR
Duckworth
W C
WC
D000818:Animals; D007339:Insulysin / Q000378:metabolism*; D010449:Peptide Mapping; D017434:Protein Structure, Tertiary; D051381:Rats; D017207:Rats, Sprague-Dawley; D013379:Substrate Specificity; D016211:Transforming Growth Factor alpha / Q000378:metabolism*
D016211:Transforming Growth Factor alpha; D007339:Insulysin