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Arabidopsis AtcwINV3 and 6 are not invertases but are fructan exohydrolases (FEHs) with different substrate specificities
Author(s) -
DE CONINCK BARBARA,
LE ROY KATRIEN,
FRANCIS ISOLDE,
CLERENS STEFAN,
VERGAUWEN RUDY,
HALLIDAY AILEEN M.,
SMITH STEVEN M.,
VAN LAERE ANDRÉ,
VAN DEN ENDE WIM
Publication year - 2005
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2004.01281.x
Subject(s) - fructan , arabidopsis , invertase , heterologous expression , arabidopsis thaliana , inulin , pichia pastoris , biochemistry , biology , heterologous , gene , mutant , enzyme , chemistry , fructose , recombinant dna
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.