title: Purification and characterization of multiple forms of the pineapple-stem-derived cysteine proteinases ananain and comosain.
abstract: A mixture of ananain (EC 3.4.22.31) and comosain purified from crude pineapple stem extract was found to contain numerous closely related enzyme forms. Chromatographic separation of the major enzyme forms was achieved after treatment of the mixture with thiol-modifying reagents: reversible modification with 2-hydroxyethyl disulphide provided enzyme for kinetic studies, and irreversible alkylation with bromotrifluoroacetone or iodoacetamide gave enzyme for structural analyses by 19F-n.m.r. and electrospray mass spectrometry respectively. Structural and kinetic analyses revealed comosain to be closely related to stem bromelain (EC 3.4.22.32), whereas ananain differed markedly from both comosain and stem bromelain. Nevertheless, differences were seen between comosain and stem bromelain in amino acid composition and kinetic specificity towards the epoxide inhibitor E-64. Differences between five isolatable alternative forms of ananain were characterized by amidolytic activity, thiol stoichiometry and accurate mass determinations. Three of the enzyme forms displayed ananain-like amidolytic activity, whereas the other two forms were inactive. Thiol-stoichiometry determinations revealed that the active enzyme forms contained one free thiol, whereas the inactive forms lacked the reactive thiol required for enzyme activity. M.s. provided direct evidence for oxidation of the active-site thiol to the corresponding sulphinic acid.
authors.affiliation: Genzyme Corporation, Cambridge, MA 02139.
authors.forename: A D
authors.initials: AD
authors.lastname: Napper
authors.forename: S P
authors.initials: SP
authors.lastname: Bennett
authors.forename: M
authors.initials: M
authors.lastname: Borowski
authors.forename: M B
authors.initials: MB
authors.lastname: Holdridge
authors.forename: M J
authors.initials: MJ
authors.lastname: Leonard
authors.forename: E E
authors.initials: EE
authors.lastname: Rogers
authors.forename: Y
authors.initials: Y
authors.lastname: Duan
authors.forename: R A
authors.initials: RA
authors.lastname: Laursen
authors.forename: B
authors.initials: B
authors.lastname: Reinhold
authors.forename: S L
authors.initials: SL
authors.lastname: Shames
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D001963:Bromelains / Q000737:chemistry; D003488:Cyanogen Bromide; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005638:Fruit / Q000201:enzymology*; D007700:Kinetics; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D017421:Sequence Analysis; D013379:Substrate Specificity
chemical_list: D010446:Peptide Fragments; D001963:Bromelains; D003546:Cysteine Endopeptidases; C066609:comosain; C057808:ananain; D003488:Cyanogen Bromide