Endo-mannanases

The most characterised D-mannan degrading enzymes are the endo- -mannanases (5). These enzymes act on a range of 1,4-p-D-mannan-type polysaccharides including D-mannan, glucomannans (acetylated and deacetylated), galactomannans and galacto-glucomannans. The extent and... 

Degradation of galactomannans with endo-mannanases usually liberates both linear and branched oligosaccharides. The branched oligosaccharides contain (1— 4)-linked-p-D-mannose residues with a single a-D-Gal/> residue (Courtois and Le Dizet, 1968). RecenUy McCleary et al. 

This enzyme [EC 3.2.1.78], also known as mannan endo-l,4-j8-mannosidase and endo-l,4-mannanase, catalyzes the random hydrolysis of l,4-j8-D-mannosidic linkages in mannans, galactomannans, glucomannans, and galacto-glucomannans. 

SOLUBILITY PRODUCT MANGANESE PEROXIDASE PEROXIDASE /3-MANNANASE MANNOSIDASES Mannan endo-1,4-j8-mannosidase, 13-MANNANASE Mannans,... 

Invertase from a Saccharomyces cerevisiae mutant could be separated into two fractions on the basis of solubility in ammonium sulfate.382 The soluble fraction reacted with endo-(l - 6)-a-mannanase, when it became insoluble. The results suggested that the insoluble fraction contained only the highly branched, core section, but the soluble fraction also had the (l->6)-a-D-mannan chain attached. 

Sprucewood holocellulose was treated with an endo-p-1,4-mannanase isolated from Aspergillus niger and an endo-/3-1,4-xylanase, two avicelases, and a cellobiohydrolase C isolated from Trichoderma viride. The mannanase hydrolyzed about a quarter of the mannan in 2-3 days without xylan or cellulose degradation. The xylanase hydrolyzed about half the xylan with 10% mannan solubilization. The three cellulases hydrolyzed up to 45% of the cellulose and 20% of the xylan, accompanied by 40-70% solubilization of the mannan. Combined xylanase-mannanase treatment hydrolyzed about half the xylan and mannan. Addition of mannanase to to cellulose-treated samples increased the degradation of the cellulose and mannan. Micromorphological studies of the variously treated specimens revealed a loss of substances in P/Slf T, and adjacent zones of S2 of the tracheid wall. 

In the present work, one of the endo-/M,4-xylanase (E.C. 3.2.1.8), the endo-/ -l,4-mannanase (E.C. 3.2.1.78), and the avicelases used in the former experiments with beechwood holocellulose (10,11) were applied to sprucewood holocellulose in order to obtain a better understanding of the individual and combined actions of these enzymes on the complex carbohydrate skeleton of wood. The experiments could be conducted only with a limited number of samples therefore, the figures given in this chapter have to be considered as preliminary results. 

The enzymes involved in depolymerization of the mannan s consist of /3-mannanase (EC 3.2.1.78), the endo-acting enzyme, and (3-mannosidase (EC 3.2.1.25), which produces... 

According to Reese and Shibata,221 the biodegradative hydrolysis of galactomannan requires at least three different enzymes, namely, a-D-galactosidase, endo-/3-D-mannanase, and j3-D-mannosidase. In addition to these enzymes, there is also a report222 of a phosphorylase, identified as oligo-j8-D-mannosyl-(l— 4)-phosphorylase, which may take part in the degradation. These enzymes will now be discussed in detail. 

Most /S-D-mannanases are endo-acting enzymes, as evidenced by a rapid fall in viscosity when they act on polymeric substrates, producing a series of D-manno-oligosaccharides of different d.p. val-... 

Endo-D-mannanases degrading galacto- and gluco-mannans usually liberate a series of mixed oligosaccharides, in addition to the linear (1 — 4)-/3-D-manno-oligosaccharides. Several of the former oligosaccharides have been isolated, and characterized (usually by methylation), and are described next. 

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