RebG- and RebM-catalyzed indolocarbazole diversification

Area of Science:

• Natural Product Biosynthesis
• Enzymology
• Medicinal Chemistry

Background:

• Rebeccamycin and staurosporine are antitumor indolocarbazole glycosides.
• RebG is a N-glucosyltransferase and RebM is a 4'-O-methyltransferase involved in their biosynthesis.

Purpose of the Study:

• To establish an efficient in vivo biotransformation system for RebG.
• To investigate the substrate promiscuity and regioselectivity of RebG and RebM.
• To evaluate the biological activity of novel indolocarbazole analogues.

Main Methods:

• Development of an in vivo biotransformation system in Streptomyces lividans and Escherichia coli.
• Bioconversion of indolocarbazole surrogates using RebG.
• In vitro 4'-O-methylation of glucosylated products using RebM.
• Cytotoxicity assays of generated analogues.

Main Results:

• RebG efficiently glucosylated various indolocarbazole surrogates.
• RebM catalyzed 4'-O-methylation of RebG products.
• Both enzymes exhibited substrate promiscuity.
• RebG showed a lack of regioselectivity with asymmetric substrates.
• 4'-O-methylation was critical for the cytotoxicity of the analogues.

Conclusions:

• The developed biotransformation system is effective for generating indolocarbazole analogues.
• RebG and RebM are versatile enzymes for creating novel antitumor compounds.
• Enzymatic modification, particularly 4'-O-methylation, is key to enhancing biological activity.