Fig. 8.
Cathepsin L cleaves dibasic and monobasic processing sites of enkephalin-containing peptide substrates bovine adrenal medulla peptide 22 (BAM-22P) and Peptide F. (a) Cathepsin L cleavage of BAM-22P: analyses of peptide products by matrix-assisted laser desorption ionization/time-of-flight (MALDI-TOF) MS. BAM-22P was incubated with cathepsin L, and monoisotopic masses (MH+, in Daltons) of peptide products are illustrated for mass peaks. The primary sequence of BAM-22P (residues 1–22) is shown, and arrows indicate cathepsin L cleavage sites. (Inset) [Met]enkephalin (ME) was readily detected by electrospray MS as well as by MALDI-TOF MS. (b) Cathepsin L cleavage of Peptide F: analyses of peptide products by MALDI-TOF MS. Cathepsin L cleavage products of Peptide F were identified by MALDI-TOF MS. Cathepsin L cleavage sites are illustrated by solid arrows above the Peptide F sequence, and the dotted-line arrows indicate secondary cleavage sites.