Journal Article

The XTH Family of Enzymes Involved in Xyloglucan Endotransglucosylation and Endohydrolysis: Current Perspectives and a New Unifying Nomenclature

Jocelyn K. C. Rose, Janet Braam, Stephen C. Fry and Kazuhiko Nishitani

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 43, issue 12, pages 1421-1435
Published in print December 2002 | ISSN: 0032-0781
Published online December 2002 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/pcp/pcf171
The XTH Family of Enzymes Involved in Xyloglucan Endotransglucosylation and Endohydrolysis: Current Perspectives and a New Unifying Nomenclature

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The polysaccharide xyloglucan is thought to play an important structural role in the primary cell wall of dicotyledons. Accordingly, there is considerable interest in understanding the biochemical basis and regulation of xyloglucan metabolism, and research over the last 16 years has identified a large family of cell wall proteins that specifically catalyze xyloglucan endohydrolysis and/or endotransglucosylation. However, a confusing and contradictory series of nomenclatures has emerged in the literature, of which xyloglucan endotransglycosylases (XETs) and endoxyloglucan transferases (EXGTs) are just two examples, to describe members of essentially the same class of genes/proteins. The completion of the first plant genome sequencing projects has revealed the full extent of this gene family and so this is an opportune time to resolve the many discrepancies in the database that include different names being assigned to the same gene. Following consultation with members of the scientific community involved in plant cell wall research, we propose a new unifying nomenclature that conveys an accurate description of the spectrum of biochemical activities that cumulative research has shown are catalyzed by these enzymes. Thus, a member of this class of genes/proteins will be referred to as a xyloglucan endotransglucosylase/hydrolase (XTH). The two known activities of XTH proteins are referred to enzymologically as xyloglucan endotransglucosylase (XET, which is hereby re-defined) activity and xyloglucan endohydrolase (XEH) activity. This review provides a summary of the biochemical and functional diversity of XTHs, including an overview of the structure and organization of the Arabidopsis XTH gene family, and highlights the potentially important roles that XTHs appear to play in numerous examples of plant growth and development.

Keywords: Keywords: Cell expansion — Cell wall — Hydrolase — Endotransglucosylase — Xyloglucan.; Abbreviations: Ara, arabinose; EXT or EXGT, endo-xyloglucan transferase (one of the previous nomenclatures used for an XTH); Fuc, fucose; Gal, galactose; Glc, glucose; Mr, relative molecular mass; O→O, oligosaccharide-to-oligosaccharide (endotransglucosylation); P→O, polysaccharide-to-oligosaccharide (endotransglucosylation); P→P, polysaccharide-to-polysaccharide (endotransglucosylation); XEH, xyloglucan endohydrolase (name of one of the two enzyme activities exhibited by XTHs); XET, formerly xyloglucan endotransglycosylase (one of the previous nomenclatures used for an XTH) — here re-defined as xyloglucan endotransglucosylase (name of one of the two enzyme activities exhibited by XTHs); XGO, xyloglucan oligosaccharide (general); XTH, xyloglucan endotransglucosylase/hydrolase (name of protein or gene); XTR, XET-related (one of the previous nomenclatures used for an XTH); XXXG, XXLG, XLLG, XXFG, XXG, XG, etc., specific XGOs (for nomenclature, see Fry et al. (1993); Xyl, xylose. The suffix “-ol” refers to XGOs that have been reduced.

Journal Article.  10507 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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