| Abstract
| - Indigoids, a class of bis-indoles, represent a promising protein kinase inhibitor scaffold.Oxidation of indole by cytochrome P450 (P450) has been shown to generate species (indoxyl,isatin) that couple to yield indigo and indirubin. Escherichia coli-expressed human P450 2A6mutants isolated from a randomized library were incubated with 27 substituted indolederivatives. Extracts of the cultures were screened for inhibition of human cyclin-dependentkinases (CDK)-1 and -5 and glycogen synthase kinase-3 (GSK3). The extracts from culturesincubated with 5-methoxyindole were the most inhibitory. High-performance liquid chromatography (HPLC) separation yielded a mixture of seven colored indigoids. These indigoidsincluded indigo, indirubin, the di(5-methoxy) derivatives of indigo and indirubin, and both ofthe possible mono 5-methoxy derivatives of indirubin, which were all identified by visible, mass,and NMR spectra. Cultures with 5-methylindole added to the media also yielded inhibitorymaterial, and 5- and 5‘-methylindirubin were characterized. The most inhibitory of theseindigoids were the monosubstituted indirubins and 5,5‘-dimethoxyindirubin, which was ≥10×more active than indirubin. Thus, the overall approach involves the use of a library ofrandomized enzyme mutants to activate component moieties of a desired set of larger molecules,thus yielding a library of drug candidates that can be screened and characterized. The generalstrategy may have additional applications.
|
