D-Glucanase

A list of entrapped enzymes is given in Table 3.2. There are two endo-l,3-P-D-glucanases from marine mollusks Spisula sacchalinensis and Ch. albidus and a-D-galactosidase from marine bacterium Pseudoalteromonas sp. MM 701. They were selected for immobilization for the following reasons ... 

Endo-1,3-P-D-glucanase Le is a highly labile enzyme. It is especially sensitive to temperature, denaturating at 25 °C. The common approaches were unsuitable for its immobilization. 

Fig. 3.10 Relative activities of endo-l,3-P-D-glucanase L V in aqueous solution (1) and in the immobilized state (2) as well as immobilized endo-l,3-P-D-glucanase L0 (3) vs. the time of testing. The enzyme entrapment was performed as described in Refs. [55,56], The silica matrix...

The decreased denaturating action of the precursor and procedure enables one to immobilize reduced amounts of biomaterial. It was demonstrated in Ref. [55] that biocatalysts prepared by entrapping endo-l,3-P-D-glucanase and a-D-galactosidasc in amounts comparable to that in living cells had a reasonable level of activity. When the TEOS is applied, the enzyme content in silica matrix can be up to 20-30 wt.% to counterbalance losses due to denaturation [50]. 

Shchipunov, Yu.A., Burtseva, Yu.V., Karpenko, T.Yu., Shevchenko, N.M. and Zvyagintseva, T.N. (2006) Highly efficient immobilization of endo-l,3-P-D-glucanases (laminarinases) from marine mollusks in novel hybrid polysaccharide silica nanocomposites with regulated composition. Journal of Molecular Catalysis B-Enzymatic, 40, 16-23. 

When T. harzianum IMI298372 was grown on cell walls of R. solani as carbon source, electrophoresis showed that a much more complex mixture of extracellular proteins was formed when the antagonist was grown on glucose (28). While both 1,3-/ -D glucanase and chitinase were induced, irrespective of whether glucose or cell walls were used as the carbon substrate, the total activity and specific activity depended on the substrate (Table II). 

Kinetic investigations were performed using the tetrasaccharide (44i), its higher homologs of DP 5 and DP 6, and 1,3 l,4-j3-D-glucanase isolated from Bacillus licheniformis [42 b]. As expected, all these compounds were resistant to enzymatic cleavage and have been shown to act as competitive inhibitors (Ki in mmol/1 range). 

Varghese and coworkers have identified the active site nucleophiles of two crystalline ) -D-glucan endohydrolases from germinating barley [70]. In more recent work, Hej and coworkers were able to introduce 2,3-epoxypropyl- -laminaribioside 8 (n = 1) into the active site of the crystalline l,3-/3-D-glucanase from barley [71]. A subsequent X-ray crystallographic investigation gave invaluable information about the active site of this enzyme and the point of attachment between enzyme and inhibitor was confirmed. 

Fig. 3. —Proposed Structure of a Portion of theHemieellulosicXyloglucan of the Primary Cell-Wall of Dicots (After Albersheim5-64). [Heptasac-charide A and nonasaccharide B are derived from oligosaccharide C by the action of endo-(l—>4)-/ -D-glucanase at the bonds indicated by arrows. Pentasaccharide D is derived from "B by the combined action of a-L-fucosidase, a-D-xylosidase, and /J-D-glucosidase. A = L-arabinopyranose F = L-fucose G = D-glucose Gal = D-galactose X = D-xylose.]...

These polymers are distinguished from cellulose by the presence of both/ -(l— 3)- and / -(l— 4)-linked D-glucosyl residues, lower molecular weights (some noncellulosic glucans are water-soluble), and susceptibility to hydrolysis by / -D-glucanases that cannot hydrolyze cellulose. Unlike cellulose, whose microfibrillar structure and structural role in the cell wall has been clearly established, the function of these polymers as structural components of the wall is still a subject of controversy there is some evidence that they are energy-reserve materials.110-201 202... 

When the extracellular, acidic polysaccharide from Rhizobium meliloti IFO 13336 was hydrolyzed with extracellular /3-D-glycanase and then intracellular endo-(l - 6)-/J-D-glucanase, two tetrasaccharides were... 

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