title: Salicortin: a repeat-attack new-mechanism-based Agrobacterium faecalis beta-glucosidase inhibitor.
abstract: Salicortin, a natural product abundant in most members of the Salicaceae family, is a mechanism-based inactivator of Agrobacterium faecalis beta-glucosidase. Inactivation is delayed in the presence of competitive inhibitors, thereby demonstrating the requirement for an enzyme-bound salicortin before inactivation. Product studies suggest that inactivation proceeds via a quinone methide intermediate formed by the fragmentation of the aglycone of salicortin while it is bound to the enzyme. Tryptic digest and HPLC/MS studies confirm the role of quinone methide attack and also show that the enzyme undergoes multiple modifications. In addition, when the inactivation was run in the presence of a mutant inactive form of the enzyme, HPLC/MS analyses clearly showed no modification of the mutant enzyme, demonstrating that the quinone methide does not exist in free solution and suggesting that inactivation is active-site directed.
authors.affiliation: Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
authors.forename: J
authors.initials: J
authors.lastname: Zhu
authors.forename: S G
authors.initials: SG
authors.lastname: Withers
authors.forename: P B
authors.initials: PB
authors.lastname: Reichardt
authors.forename: E
authors.initials: E
authors.lastname: Treadwell
authors.forename: T P
authors.initials: TP
authors.lastname: Clausen
mesh_terms: D017485:1-Deoxynojirimycin / Q000494:pharmacology; D001667:Binding, Competitive / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005960:Glucosides / Q000737:chemistry* / Q000494:pharmacology*; D007700:Kinetics; D013058:Mass Spectrometry; D015394:Molecular Structure; D010940:Plant Proteins / Q000378:metabolism; D012231:Rhizobium / Q000201:enzymology*; D001617:beta-Glucosidase / Q000037:antagonists & inhibitors*
chemical_list: D004791:Enzyme Inhibitors; D005960:Glucosides; D010940:Plant Proteins; D017485:1-Deoxynojirimycin; D001617:beta-Glucosidase; C113068:salicortin