Synthesis of fructans by fructosyltransferase from the tuberous roots of Viguiera discolor (Asteraceae)

Abstract

Sucrose:sucrose fructosyltransferase (SST) and fructan:fructan fructosyl-transferase (FFT) activities from crude extracts of tuberous roots of Viguiera discolor growing in a preserved area of cerrado were analyzed in 1995-1996. SST activity was characterized by the synthesis of 1-kestose from sucrose and FFT activity by the production of nystose from 1-kestose. The highest fructan-synthesizing activity was observed during early dormancy (autumn), when both (SST and FFT) activities were high. The increase in synthetic activity seemed to start during the fruiting phase in the summer, when SST activity was higher than in spring. During winter and at the beginning of sprouting, both activities declined. The in vitro synthesis of high molecular mass fructans from sucrose by enzymatic preparations from tuberous roots collected in summer showed that long incubations of up to 288 h produced consistently longer polymers which resembled those found in vivo with respect to chromatographic profiles.

Fructan degradation and hydrolytic activity in tuberous roots of Viguiera discolor Baker (Asteraceae), a herbaceous species from the cerrado

“…Indeed, 1-FFT from other Asteraceae has been shown to be a concanavalin A binding glycoprotein and this probably explains why this contamination follows 1-FEH throughout purification. Besides, as shown previously, 1-FFT activity is present during all the annual growth cycle of V. discolor (Itaya et al 1999).…”

“…DX 300 (USA), according to Itaya et al (1999). Sugars were identified by cochromatography with authentic standards.…”

Produção de concentrados de frutose por inulinases de Penicillium janczewskii e atividade sobre o nível de glicose plasmática em ratos diabéticos

“…Uma alternativa para esse processo é a hidrólise da inulina, polímero de frutose encontrado como carboidrato de reserva em várias plantas da família asterácea, como Cichorium intybus e Helianthus tuberosus [17,27] e em espécies nativas do cerrado brasileiro, como Vernonia herbacea e Viguiera discolor, sendo que nestas últimas cerca de 80% da massa seca de seus órgãos subterrâneos são constituídos por inulina [11,14]. Para a obtenção de frações com características biológicas similares, derivadas do polissacarídeo inulina, é importante a utilização de um método que permita a diminuição do grau de polimerização do polissacarídeo sem, contudo, modificar suas características estruturais, para que a ação biológica não seja afetada.…”

Transport of 1-kestose across the tonoplast of Jerusalem artichoke tubers

“…This step is catalyzed by sucrose:sucrose fructosyl transferase (1-SST; EC 2.4.1.99), a vacuolar enzyme isolated and purified from a wide variety of tissues (Pollock and Suzuki, 1986;Praznik et al, 1990;Angenent et al, 1993;Koops and Jonker, 1996;. Although demonstrated both in vivo (Cairns et al, 1989;Hellwege et al, 1997) and in vitro (Bancal and Gaudillere, 1993;Cairns, 1993;Penson and Cairns, 1994;Lu¨scher et al, 1996;Itaya et al, 1997;Vijn et al, 1998), synthesis of 1-kestose by 1-SST has remained ambiguous in light of the enzyme's unusually high K m for sucrose which varies from 75 mM up to over 500 mM depending on the tissue investigated and assay conditions (Chatterton et al, 1988;Cairns and Ashton, 1994). For example, in developing Jerusalem artichoke tubers, the K m for sucrose has been estimated to be approximately 500 mM (Koops and Jonker, 1996).…”

“…Recent reports of in vitro fructan synthesis (Bancal and Gaudillere, 1993;Cairns, 1993Cairns, , 1999Penson and Cairns, 1994;Itaya et al, 1997) also carried the inherent inefficiencies of 1-SST as sucrose concentrations of 50-800 mM were required. The in vivo synthesis of 1-kestose by transformed potato tubers (Hellwege et al, 1997) was facilitated by the higher vacuolar sucrose concentration and by long term incubation.…”