Indolyl Septanoside Synthesis for In Vivo Screening of Bacterial Septanoside Hydrolases

• Main Authors: Aditya R. Pote, Sergi Pascual, Antoni Planas, Mark W. Peczuh
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: International Journal of Molecular Sciences
• Subjects: septanoside; indolyl glycoside; glycosidase; septanoside hydrolase
• Online Access: https://www.mdpi.com/1422-0067/22/9/4497

Building-up and breaking-down of carbohydrates are processes common to all forms of life. Glycoside hydrolases are a broad class of enzymes that play a central role in the cleavage of glycosidic bonds, which is fundamental to carbohydrate degradation. The large majority of substrates are five- and six-membered ring glycosides. Our interest in seven-membered ring septanose sugars has inspired the development of a way to search for septanoside hydrolase activity. Described here is a strategy for the discovery of septanoside hydrolases that uses synthetic indolyl septanosides as chromogenic substrates. Access to these tool compounds was enabled by a route where septanosyl halides act as glycosyl donors for the synthesis of the indolyl septanosides. The screening strategy leverages the known dimerization of 3-hydroxy-indoles to make colored dyes, as occurs when the β-galactosidase substrate X-Gal is hydrolyzed. Because screens in bacterial cells would enable searches in organisms that utilize heptoses or from metagenomics libraries, we also demonstrate that septanosides are capable of entering <i>E. coli</i> cells through the use of a BODIPY-labeled septanoside. The modularity of the indolyl septanoside synthesis should allow the screening of a variety of substrates that mimic natural structures via this general approach.