Ceratocystis paradoxa

Fig. 22.— 13C-N.m.r. Spectra of Polysaccharides from Ceratocystis paradoxa (A) and the Preponderant Glucomannan from Ceratocystis hrunnea (B). (Solvent, DjO temperature, 70° chemical shifts expressed as 8C, relative to external tetramethylsilane.)...

From rate and product studies with xylooligosaccharides it was concluded that a xylanase from Ceratocystis paradoxa requires a chain of at least five xylose residues for rapid binding and subsequent hydrolysis (18). The catalytic site is assumed to be situated asymmetrically within a row of the five binding subsites. Similar studies on a cellulase from Aspergillus niger also suggest the presence of five binding subsites (14). 

The molecular weights of D-xylanase preparations of different origins (see Table XXII), like those of the other hemicellulases (see Sections II, III, and IV), are relatively low, ranging from 16,000 to 38,000. The pi values reported for several D-xylanases are also shown in Table XXII, and, with the exception of the Ceratocystis paradoxa D-xylanase I (Ref. 228) (pi 9.17), are mainly acid gly-canases. 

Whether this is true for the other purified D-xylanase preparations is not yet known, as, in most cases, the pi values have not been reported, but it appears equally possible that neutral (for example, Fomes annosus,61 pi = 7.0), and alkaline (for example, Ceratocystis paradoxa 228 pi = 9.17) D-xylanases also exist. The Km values of several fungal D-xylanases have been reported (see Table XXII) and... 

Degradation products arising from the hydrolysis of arabinoxylo-and xylo-oligosaccharides of d.p. 3-6 and 2-5, respectively, by the action of a D-xylanase (HC I) from Ceratocystis paradoxa are shown in Table XXIV. Xylotetraose (X4) was the smallest xylo-oligosaccharide attacked, and both it and X5 yielded X2 and X3. The mechanism proposed228 for the hydrolysis of X4 by HC I is as follows. 

Trisaccharide X3 was the lowest homologue attacked, liberating D-xylose and X2, whereas AX3 yielded AX2 and D-xylose.236 The mode of action of Ceratocystis paradoxa xylanase HC II on arabinoxylo- and xylo-oligosaccharides is as shown it indicates that attack occurs at the reducing end of the oligosaccharide chain. 

Proposed structure (see Refs. 228, 236, and 249) from the results of the action of the endo-D-xylanases (HC I and HC II) from Ceratocystis paradoxa on this oligosaccharide. 

Figure 5. Partial NMR spectra of galactofuranose-containing polysaccharides in (A) glucomannan and mannan from Ceratocystis paradoxa and (B) gluco-mannan from Ceratocystis brunnea...

Ceratocystis paradoxa Fungi OA, EtOH. 3 days. 20X 20,000 Narasimba Rao et al. (1971)... 

---