title: Identification of the reactive cysteine residues in oligopeptidase B from Trypanosoma brucei.
abstract: Oligopeptidase B (OpdB) from Trypanosoma brucei is a candidate therapeutic target in African trypanosomiasis. OpdB is an atypical serine peptidase, since activity is inhibited by thiol-blocking reagents and enhanced by reducing agents. We have identified C256 as the reactive cysteine residue that mediates OpdB inhibition by N-ethylmaleimide and iodoacetic acid. Modeling studies suggest that C256 adducts occlude the P(1) substrate-binding site, preventing substrate binding. We further demonstrate that C559 and C597 are responsible for the thiol-enhancement of OpdB activity. These studies may facilitate the development of specific OpdB inhibitors with therapeutic potential, by exploiting these unique properties of this enzyme.
authors.affiliation: Department of Internal Medicine, University of Giessen School of Medicine, Aulweg 123 (Room 6-11), D-35392 Giessen, Germany. rory.morty@inmere.med.uni-giessen.de
authors.forename: Rory E
authors.initials: RE
authors.lastname: Morty
authors.forename: Angela Y
authors.initials: AY
authors.lastname: Shih
authors.forename: Vilmos
authors.initials: V
authors.lastname: Fülöp
authors.forename: Norma W
authors.initials: NW
authors.lastname: Andrews
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003545:Cysteine / Q000378:metabolism*; D017931:DNA Primers; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000201:enzymology*
chemical_list: D017931:DNA Primers; D012697:Serine Endopeptidases; C090703:oligopeptidase B; D003545:Cysteine