title: Comparative study on the active sites of ficin and papain by the spin labeling method.
abstract: Ficin was alkylated with a series of haloacetamide spin labels with various distances between the spin probes and reactive groups. From the relation of these distances to the tau c values of the labels incorporated into protein, it was estimated that the depth of the active site hole of ficin is ca. 8 A. The results are somewhat different from those reported previously for papain (S. Nakayama et al. (1981) Biochem. Biophys. Res. Commun. 98, 471-475). Examination of the pH dependence of the ESR spectra for ficin and papain alkylated with an iodoacetamide or a maleimide spin label suggested that these enzymes have an amino acid residue of pKa 4 (probably a histidine residue) around the active site cysteine and that the active site conformations change at around pH 5.
authors.affiliation: University of Library and Information Science, Ibaraki.
authors.forename: S
authors.initials: S
authors.lastname: Nakayama
authors.forename: T
authors.initials: T
authors.lastname: Watanabe
authors.forename: K
authors.initials: K
authors.lastname: Takahashi
authors.forename: M
authors.initials: M
authors.lastname: Hoshino
authors.forename: M
authors.initials: M
authors.lastname: Yoshida
mesh_terms: D001665:Binding Sites; D003546:Cysteine Endopeptidases / Q000032:analysis*; D004578:Electron Spin Resonance Spectroscopy; D005361:Ficain / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D010206:Papain / Q000032:analysis*; D011487:Protein Conformation; D013113:Spin Labels
chemical_list: D013113:Spin Labels; D003546:Cysteine Endopeptidases; D010206:Papain; D005361:Ficain