title: Baicalin and scutellarin are proteasome inhibitors that specifically target chymotrypsin-like catalytic activity.
abstract: Baicalin and scutellarin are the major active principal flavonoids extracted from the Chinese herbal medicines Scutellaria baicalensis and Erigeron breviscapus (Vant.) Hand-Mazz. It has recently been reported that baicalin and scutellarin have antitumor activity. However, the mechanisms of action are unknown. We previously reported that some flavonoids have a specific role in the inhibition of the activity of proteasome subunits and induced apoptosis in tumor cells. To further investigate these pharmacological effects, we examined the inhibitory activity of baicalin and scutellarin on the extracted proteasomes from mice and cancer cells. Using fluorogenic substrates for proteasome catalytic subunits, we found that baicalin and scutellarin specifically inhibited chymotrypsin-like activity but did not inhibit trypsin-like and peptidyl-glutamyl peptide hydrolyzing activities. These data suggested that baicalin and scutellarin specifically inhibit chymotrypsin-like catalytic activity in the proteasome.
authors.affiliation: Department of Biochemistry, Hamamatsu University School of Medicine, Hamamatsu, Japan. yixinwu@hama-med.ac.jp
authors.forename: Yi-Xin
authors.initials: YX
authors.lastname: Wu
authors.forename: Eiji
authors.initials: E
authors.lastname: Sato
authors.forename: Wataru
authors.initials: W
authors.lastname: Kimura
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Miura
mesh_terms: D000818:Animals; D047310:Apigenin / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival; D002918:Chymotrypsin / Q000037:antagonists & inhibitors*; D049919:Erigeron / Q000737:chemistry; D005260:Female; D005419:Flavonoids / Q000494:pharmacology*; D005965:Glucuronates / Q000494:pharmacology*; D006801:Humans; D008099:Liver / Q000201:enzymology; D051379:Mice; D008813:Mice, Inbred ICR; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects; D061988:Proteasome Inhibitors / Q000494:pharmacology*; D031364:Scutellaria baicalensis / Q000737:chemistry
chemical_list: D005419:Flavonoids; D005965:Glucuronates; D061988:Proteasome Inhibitors; C484876:scutellarin; C038044:baicalin; D047310:Apigenin; D002918:Chymotrypsin; D046988:Proteasome Endopeptidase Complex
keywords: baicalin; flavonoid; inhibitor; proteasome; scutellarin