Chapter 10 - Glycoside hydrolase family 16—Xyloglucan:xyloglucosyl transferases and their roles in plant cell wall structure and mechanics

Abstract

Plant xyloglucan:xyloglucosyl transferases also known as xyloglucan endo-transglycosylases (XETs) are classified in the glycoside hydrolase family 16. This family includes enzymes with a β-jelly-roll fold, which underlies their broad substrate specificity, and the catalytic function to mediate transglycosylation reactions with xyloglucan (XG)-derived or other substrates. This relaxed substrate specificity stems from structural plasticity and plays a fundamental role in plant cell wall remodeling and mechanics that have evolved to operate in various monophyletic groups. XET enzymes occur in gene families that underlie the synthesis of functional proteins in time- and space-dependent means and during plant development stresses caused by biotic and ecological stimuli. In this chapter, we focus on XETs and how their singularly carbohydrate-based enzymatic function underlies linking the diverse and complex structures of plant cell walls. We conclude that broad substrate nonspecific XETs are plant-prevalent and that these enzymes play roles in targeted cell wall modifications.