The genome of Arabidopsis thaliana contains six putative cell-wall type invertase genes (AtcwINV1-6). Heterologous expression of AtcwINV1, 3 and 6 cDNAs in Pichia pastoris revealed that the enzymes encoded by AtcwINV3 and 6 did not show invertase activity. Instead, AtcwINV3 is a 6-FEH and AtcwINV6 is a fructan exohydrolase (FEH) that can degrade both inulin and levan-type fructans. For AtcwINV6 it is proposed to use the term (6&1) FEH. In contrast, AtcwINV1 is a typical invertase. FEH activity was also detected in crude extracts of different parts of Arabidopsis. To verify that the FEH activity of AtcwINV3 and 6 were not artefacts of the heterologous expression system, the protein corresponding to AtcwINV3 was isolated from whole Arabidopsis plants and indeed showed only 6-FEH activity and no invertase activity. Although no fructans can be detected in Arabidopsis plants, it is shown that kestoses (trimers) can be synthesized in crude leaf extracts. The putative physiological significance of FEH in so-called non-fructan plants is discussed.

Item Type:	Refereed Article
Keywords:	Pichia pastoris, Arabidopsis, cell-wall inver-tase, defence, inulin, levan
Research Division:	Biological Sciences
Research Group:	Plant Biology
Research Field:	Plant Physiology
Objective Division:	Expanding Knowledge
Objective Group:	Expanding Knowledge
Objective Field:	Expanding Knowledge in the Biological Sciences
Author:	Smith, SM (Professor Steven Smith)
ID Code:	101521
Year Published:	2005
Web of Science® Times Cited:	81
Deposited By:	Plant Science
Deposited On:	2015-06-25
Last Modified:	2015-09-27
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