A Review of XET Enzymes, Current Applications
and Future Trends
Gurpreet Kaur
Abstract:- Xyloglucanis a well-known plant polymer and has been used in the textile industry as a sizing agent. The enzyme xyloglucanendotransglycosylase/hydrolase (XET) has become important in the last 25 years for understanding the plant growth system. The discovery of various XET enzymes and understanding their role in cell wall metabolism in plants lead towards its application in various fields. Cloning and expression of many different XET enzymes in industrially important microbes paved way for producing sufficient quantities of the enzyme that was essential for further studies. The uniqueness of XET enzymes in terms of introducing groups through xyloglu can eventualized their usage in surface modification of cellulosic substrates. This review article provides a compilation of most of the XET enzymes reported and the associated applications. The article also provides a complete list of patents listed till date that reported the XGO-XET system for an application involving surface modification. The possibility of future trends in wider areas where XET enzymes could be used is also discussed.
I. INTRODUCTION
Ever since the first documentation of the xyloglucanendotransglucosylase/hydrolase (XTH/XET) enzymes about three decades ago [1], [2] they have been an important class of enzymes with respect to understanding several mechanisms in plants. The unique mechanism of XET enzymes enables them to hydrolyse and re-ligate the xyloglucan oligosaccharide to other xyloglucanoligosachharide/polysachharide chains [3]. The xyloglucan molecules have strong tendency to bind naturally with cellulose chains via hydrogen bonds and hydrophobic interactions in vivo [4] and in vitro the xyloglucan molecules bind almost instantaneously with cellulose. The interaction of xyloglucan with cellulose plays a key role in controlling the growth of plant cells, fruit softening, response to pathogens and vascular differentiation [5]. Different isozymes of the XTH enzymes are expressed at different stages of plant/fruit growth [6].