Efforts Towards Understanding the Formation of the Eurekanate Sugar and the Early Biosynthesis of Everninomicin D

Abstract

Everninomicin D is a potent orthosomycin antibiotic that has a unique binding site on the 50S ribosome allowing it to inhibit protein synthesis without any cross-resistance due to other ribosome-targeting antibiotics. The biosynthesis of this complex octasaccharide, as produced by Micromonospora carbonacea var. aurantiaca, has been studied in the Vanderbilt Laboratory for Biosynthetic Studies for a number of years in order to understand how the bacteria produces this compound and to enable development of analogs along the scaffold. The project discussed herein has focused on understanding the biosynthesis of the eurekanate sugar, the eastern terminal sugar of everninomicin D. Eurekanate is the most functionalized sugar in the scaffold being that it is branched by the addition of two carbons, which is a very rare sugar modification, and that it contains an orthoester linkage and the methylene dioxybridge. In the study of this sugar, a series of genetic deletions within the producing organism began to clarify that the biosynthesis of eurekanate happens very early on in the biosynthesis of everninomicin D, and is in fact integral to the continuation of this biosynthetic pathway. To study the early formation of eurekanate in vivo, a glucuronic acid decarboxylase was identified and fully characterized, including characterization of the two products produced as well as crystal structure elucidation. Overall, this project aimed to identify and characterize the enzymes responsible for the formation of eurekanate and their overall timing within the biosynthesis of everninomicin D.