Enhancement of cellulose production by expression of sucrose synthase in Acetobacter xylinum

Abstract

Higher plants efficiently conserve energy ATP in cellulose biosynthesis by expression of sucrose synthase, in which the high free energy between glucose and fructose in sucrose can be conserved and used for the synthesis of UDP-glucose. A mixture of sucrose synthase and bacterial cellulose synthase proceeded to form UDP-glucose from sucrose plus UDP and to synthesize 1,4-␤-glucan from the sugar nucleotide. The mutant sucrose synthase, which mimics phosphorylated sucrose synthase, enhanced the reaction efficiency (V max ͞K m ) on 1,4-␤-glucan synthesis, in which the incorporation of glucose from sucrose was increased at low concentrations of UDP. Because UDP formed after glucosyl transfer can be directly recycled with sucrose synthase, UDPglucose formed appears to show high turnover with cellulose synthase in the coupled reaction. The expression of sucrose synthase in Acetobacter xylinum not only changed sucrose metabolism but also enhanced cellulose production, in which UDP-glucose was efficiently formed from sucrose. Although the level of UDP-glucose in the transformant with mutant sucrose synthase cDNA was only 1.6-fold higher than that in plasmid-free cells, the level of UDP was markedly decreased in the transformant. The results show that sucrose synthase serves to channel carbon directly from sucrose to cellulose and recycles UDP, which prevents UDP build-up in cellulose biosynthesis.

Sucrose synthase affects carbon partitioning to increase cellulose production and altered cell wall ultrastructure

“…Similarly, in other plant species, the level of SuSy expression has been shown to be associated strongly with cellulose synthesis. Expression of the modified mung bean SuSy (S11E) in Acetobacter xylinum caused enhanced cellulose production by preventing the accumulation of UDP, which is known to inhibit cellulose formation in A. xylinum (35,11). In addition, carrot plants with suppressed SuSy showed decreased cellulose content (22), whereas suppression of SuSy in cotton resulted in an almost fiberless phenotype (36).…”

Phosphorylation of the Amino Terminus of Maize Sucrose Synthase in Relation to Membrane Association and Enzyme Activity

“…These observations may be particularly relevant toward explaining previous variability and negligible effects of phosphorylation on activity because all prior studies were performed at near neutral pH Winter et al, 1997;Nakai et al, 1998Nakai et al, , 1999Anguenot et al, 1999;Zhang et al, 1999;Chikano et al, 2001;Tanase et al, 2002). In studies in which an effect of phosphorylation on enzymatic activity was noted, it was the Suc cleavage activity of SUS that was specifically affected Nakai et al, 1998Nakai et al, , 1999Anguenot et al, 1999;Tanase et al, 2002). Our data suggest that the stimulation of cleavage activity by phosphorylation of S15 may be related to unstructuring of the amino terminus that also occurs in response to low pH (Figs.…”

“…Several studies have noted that the Suc cleavage, but not synthetic, activity of SUS is specifically affected by phosphorylation, often as a result of an increased affinity for Suc and/or UDP Nakai et al, 1998Nakai et al, , 1999Anguenot et al, 1999;Tanase et al, 2002). However, effects of phosphorylation on enzymatic activity have not been universally observed or the detected changes were minor and therefore interpreted as inconsequential (Winter et al, 1997;Zhang et al, 1999;Chikano et al, 2001).…”

Sucrose Synthase Catalyzes the de novo Production of ADPglucose Linked to Starch Biosynthesis in Heterotrophic Tissues of Plants

“…Whilst the abundance of SS in the Golgi apparatus and plasma membranes has recently evoked the idea that it is involved in directing the carbon flow to cell wall synthesis (Amor et al 1995, Nakai et al 1999) the major role commonly attributed to this enzyme in sink organs is to convert the Suc imported from leaves into UDPglucose (UDPG), which is then transformed stepwise to glucose-1-phosphate (G1P), glucose-6-phosphate (G6P) and ADPglucose (ADPG) necessary for starch biosynthesis (Fig. 1a, b) (Müller-Röber et al 1992, Okita 1992, ap Rees 1995, Villand and Kleczkowski 1994, Denyer et al 1996, Buchanan et al 2000, Kossmann and Lloyd 2000, Neuhaus and Emes 2000, Tauberger et al 2000, Tiessen et al 2002.…”