How to extend your (polylactosamine) antennae

Matthew S Kimber

doi:10.1016/j.jbc.2020.100212

Abstract

The elongated antennae decorating eukaryotic glycans are built from polylactosamine repeats. Polylactosamine forms a lectin recognition site and also acts as a platform for presenting diverse additional modifications (e.g., terminal cell-surface antigens); it therefore plays important roles in cell adherence, development, and immunity. Two new papers present a detailed structural and mechanistic investigation of β1-3-N-acetylgucosaminyltransferase 2, a key enzyme in antennae synthesis. The resulting insights will also help decipher other members of GT31, the single largest human glycosyltransferase family.

Highlights

Glycans are synthesized by the sequential addition of monosaccharide units from nucleotide phosphate donors by enzymes known as glycosyltransferases (GTs)
by β1-3-N-acetylgucosaminyltransferase (B3GNT) has seven isoforms termed B3GNT2–B3GNT8; these differ in their tissue distribution and substrate preferences, with many having specialized roles
In a pair of papers published in JBC, Hao et al (6) and Kadirvelraj et al (7) report the structure of the GT domain of B3GNT2, coupled with an in-depth analysis of the enzyme’s mechanism

Summary

Introduction

Glycans are synthesized by the sequential addition of monosaccharide units from nucleotide phosphate donors by enzymes known as glycosyltransferases (GTs). B3GNT2 is a widely expressed, membrane-anchored, Golgi-resident enzyme that appears to be the most important homolog in elongating polylactosamine (5). Challenges of working with these enzymes have resulted in many key aspects of their biochemistry—including their structure, substrate recognition modes, and catalytic mechanism—being little understood. In a pair of papers published in JBC, Hao et al (6) and Kadirvelraj et al (7) report the structure of the GT domain of B3GNT2, coupled with an in-depth analysis of the enzyme’s mechanism.

Results

Conclusion