The enzymology of fructan polymerization and depolymerization has been examined in only a few grass species, although many members of the order Poales contain fructans. The fructans present in grasses are complex compared to those stored in dicotyledonous plants. Fructans isolated from grasses include: i) the simple series of linear p-2,6-linked fructosyl units found in Poa ampla (1); ii) the predominantly p-2,6-linked fructans with limited branch points elaborated from neokestose, as found in Avena sativa and Lolium species (2,3,4), or elaborated from 6-kestose as found in Dactylis glomerata (5) , iii) the more highly branched fructans with mixtures of (3-2,1 and P-2,6- fructosyl units and a terminal glucose such as those found in Triticum aestivum (6,7) and Hordeum vulgare (8). Furthermore, it appears that many grass species contain fructans made from more than one trisaccharide, although often one fructan series predominates (1). The complexity of grass fructans and the general lack of commercial availability of these fructans have hindered rapid advancements in understanding the enzymology of fructan synthesis and mobilization in grasses. In spite of these technical limitations, significant progress has been made since previous reviews (9,10,11,12). Notably, elucidation of the enzymology of fructan synthesis and degradation has progressed due to the successful purification and cloning of several enzymes primarily from barley; accordingly, this review will focus upon these studies.
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