title: Inhibition of cathepsin E by alpha 2-macroglobulin and the resulting structural changes in the inhibitor.
abstract: The activity of cathepsin E (M(r) approximately 80K), a dimeric aspartic proteinase with two active sites per molecule, toward a protein substrate (reduced and carboxymethylated ribonuclease A) was shown to be completely inhibited by alpha 2-macroglobulin (alpha 2M) at pH 5.5. On the other hand, the activity toward a peptide substrate (oxidized insulin B chain) was scarcely inhibited. Under these conditions, cathepsin E cleaved alpha 2M at the Phe684-Tyr685 bond in the bait region sequence, resulting in a drastic conformational change (from a doughnut to an H shape) in the inhibitor as revealed by electron microscopy, and was non-covalently trapped by alpha 2M in an approximate molar ratio (enzyme: alpha 2M) of 2:1.
authors.affiliation: Department of Biophysics and Biochemistry, Faculty of Science, University of Tokyo.
authors.forename: S B
authors.initials: SB
authors.lastname: Athauda
authors.forename: H
authors.initials: H
authors.lastname: Arakawa
authors.forename: M
authors.initials: M
authors.lastname: Nishigai
authors.forename: T
authors.initials: T
authors.lastname: Takahashi
authors.forename: A
authors.initials: A
authors.lastname: Ikai
authors.forename: K
authors.initials: K
authors.lastname: Takahashi
mesh_terms: D000595:Amino Acid Sequence; D020059:Cathepsin E; D002403:Cathepsins / Q000037:antagonists & inhibitors*; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D010649:Phenylalanine / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry; D000511:alpha-Macroglobulins / Q000737:chemistry / Q000494:pharmacology* / Q000648:ultrastructure
chemical_list: D000511:alpha-Macroglobulins; D014443:Tyrosine; D010649:Phenylalanine; D002403:Cathepsins; D020059:Cathepsin E