Hetero‐trans‐β‐glucanase, an enzyme unique to <i>Equisetum</i> plants, functionalizes cellulose

Simmons, Thomas J.; Mohler, Kyle E.; Holland, Claire; Goubet, Florence; Franková, Lenka; Houston, Douglas R.; Hudson, Andrew; Meulewaeter, Frank; Fry, Stephen C.

doi:10.1111/tpj.12935

Cited by 49 publications

(101 citation statements)

References 53 publications

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“…2b,c). Such turnover was more than 10 times slower than the XET and MXE activities of EfHTG22, but was on the same order as the XET activity of AtXTH3 (Fig. 2c).…”

Section: Resultsmentioning

confidence: 80%

The plant cell-wall enzyme AtXTH3 catalyses covalent cross-linking between cellulose and cello-oligosaccharide

Shinohara

Sunagawa

Tamura

et al. 2017

Sci Rep

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Cellulose is an economically important material, but routes of its industrial processing have not been fully explored. The plant cell wall – the major source of cellulose – harbours enzymes of the xyloglucan endotransglucosylase/hydrolase (XTH) family. This class of enzymes is unique in that it is capable of elongating polysaccharide chains without the requirement for activated nucleotide sugars (e.g., UDP-glucose) and in seamlessly splitting and reconnecting chains of xyloglucan, a naturally occurring soluble analogue of cellulose. Here, we show that a recombinant version of AtXTH3, a thus far uncharacterized member of the Arabidopsis XTH family, catalysed the transglycosylation between cellulose and cello-oligosaccharide, between cellulose and xyloglucan-oligosaccharide, and between xyloglucan and xyloglucan-oligosaccharide, with the highest reaction rate observed for the latter reaction. In addition, this enzyme formed cellulose-like insoluble material from a soluble cello-oligosaccharide in the absence of additional substrates. This newly found activity (designated “cellulose endotransglucosylase,” or CET) can potentially be involved in the formation of covalent linkages between cellulose microfibrils in the plant cell wall. It can also comprise a new route of industrial cellulose functionalization.

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“…2b,c). Such turnover was more than 10 times slower than the XET and MXE activities of EfHTG22, but was on the same order as the XET activity of AtXTH3 (Fig. 2c).…”

Section: Resultsmentioning

confidence: 80%

The plant cell-wall enzyme AtXTH3 catalyses covalent cross-linking between cellulose and cello-oligosaccharide

Shinohara

Sunagawa

Tamura

et al. 2017

Sci Rep

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“…Another possibility is that hotspots are formed enzymatically. Recent reports have identified enzymes (xyloglucan endotransglucosylase/hydrolase) that can cut noncrystalline cellulose and ligate xyloglucan onto the cellulose end (Hrmova et al, 2007;Simmons et al, 2015;Shinohara et al, 2017). The specific activity of these enzymes in performing such hetero-transglucosylations is very low, so the biological significance of such reactions is uncertain.…”

Section: Cell Wall Models Need Further Refinement and Testingmentioning

confidence: 99%

Diffuse Growth of Plant Cell Walls

2017

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“…Another difference is that lichenase requires the (1→3) bond [67], whereas β-(1→3)-linkages are clearly not a requirement for the activity of HTG since it can cleave xyloglucan and cellulose [62], which lack (1→3) bonds [2]. …”

Section: Discussionmentioning

confidence: 99%

Bonds broken and formed during the mixed-linkage glucan : xyloglucan endotransglucosylase reaction catalysed by Equisetum hetero-trans-β-glucanase

Simmons

Fry

2017

Biochemical Journal

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Mixed-linkage glucan∶xyloglucan endotransglucosylase (MXE) is one of the three activities of the recently characterised hetero-trans-β-glucanase (HTG), which among land plants is known only from Equisetum species. The biochemical details of the MXE reaction were incompletely understood — details that would promote understanding of MXE's role in vivo and enable its full technological exploitation. We investigated HTG's site of attack on one of its donor substrates, mixed-linkage (1→3),(1→4)-β-d-glucan (MLG), with radioactive oligosaccharides of xyloglucan as the acceptor substrate. Comparing three different MLG preparations, we showed that the enzyme favours those with a high content of cellotetraose blocks. The reaction products were analysed by enzymic digestion, thin-layer chromatography (TLC), high-pressure liquid chromatography (HPLC) and gel-permeation chromatography (GPC). Equisetum HTG consistently cleaved the MLG at the third consecutive β-(1→4)-bond following (towards the reducing terminus) a β-(1→3)-bond. It then formed a β-(1→4)-bond between the MLG and the non-reducing terminal glucose residue of the xyloglucan oligosaccharide, consistent with its xyloglucan endotransglucosylase/hydrolase subfamily membership. Using size-homogeneous barley MLG as the donor substrate, we showed that HTG does not favour any particular region of the MLG chain relative to the polysaccharide's reducing and non-reducing termini; rather, it selects its target cellotetraosyl unit stochastically along the MLG molecule. This work improves our understanding of how enzymes can exhibit promiscuous substrate specificities and provides the foundations to explore strategies for engineering novel substrate specificities into transglycanases.

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Hetero‐trans‐β‐glucanase, an enzyme unique to Equisetum plants, functionalizes cellulose

Cited by 49 publications

References 53 publications

The plant cell-wall enzyme AtXTH3 catalyses covalent cross-linking between cellulose and cello-oligosaccharide

The plant cell-wall enzyme AtXTH3 catalyses covalent cross-linking between cellulose and cello-oligosaccharide

Diffuse Growth of Plant Cell Walls

Bonds broken and formed during the mixed-linkage glucan : xyloglucan endotransglucosylase reaction catalysed by Equisetum hetero-trans-β-glucanase

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