The Retaining Pse5Ac7Ac Pseudaminyltransferase KpsS1 Defines a Previously Unreported glycosyltransferase family (GT118)

Abstract

Cell surface sugar 5,7‐diacetyl pseudaminic acid (Pse5Ac7Ac) is a bacterial analogue of the ubiquitous sialic acid, Neu5Ac, and contributes to the virulence of a number of multidrug resistant bacteria, including ESKAPE pathogens Pseudomonas aeruginosa, and Acinetobacter baumannii. Despite its discovery in the surface glycans of bacteria over thirty years ago, to date no glycosyltransferase enzymes (GTs) dedicated to the synthesis of a pseudaminic acid glycosidic linkage have been unequivocally characterised in vitro. Herein we demonstrate that A. baumannii KpsS1 is a dedicated pseudaminyltransferase enzyme (PseT) which constructs a Pse5Ac7Ac‐a(2,6)‐Glcp linkage, and proceeds with retention of anomeric configuration. We utilise this PseT activity in tandem with the biosynthetic enzymes required for CMP‐Pse5Ac7Ac assembly, in a two‐pot, seven enzyme synthesis of an a‐linked Pse5Ac7Ac glycoside. Due to its unique activity and protein sequence, we also assign KpsS1 as the prototypical member of a previously unreported GT family (GTXXX).

KpsS1 Mediates the Glycosylation of Pseudaminic Acid in Acinetobacter Baumannii

“…During the course of our study, a report showed that KpsS1 was able to glycosylate Pse in an in vitro enzymatic reaction. [5] Our study, however, provides directed evidence of the in vivo role of this enzyme in A. baumannii, which complements very well with the recent report.…”