Degradation of larchwood xylan by enzymes of a thermophilic fungus, Thermoascus aurantiacus

Khandke, Kiran M and Vithayathil, PJ and Murthy, SK (1989) Degradation of larchwood xylan by enzymes of a thermophilic fungus, Thermoascus aurantiacus. In: Archives of Biochemistry and Biophysics, 274 (2). pp. 501-510.

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Abstract

Proteins from the culture filtrates of Thermoascus aurantiacus grown on paper were found to hydrolyze larchwood xylan completely to form xylose and $4-O-methyl-\alpha-_D-glucuronic$ acid. Partial hydrolysis of xylan by a xylanase purified from the culture filtrates resulted in the formation of neutral xylooligosaccharides of dp from 2 to 6 and acidic xylooligosaccharides of dp from 5 to 8. Each of these acidic sugars contained a single molecule of $4-O-methyl-\alpha-_D-glucuronic$ acid as a branch. Extensive hydrolysis of these oligosaccharides or xylan by xylanase led to the isolation of xylose, xylobiose, and an aldotetrauronic acid as terminal products. The structure of the aldotetrauronic acid was established by NMR as $(2^2-O-\alpha-_D,4-O-methyl-\alpha-_D-glucurono)-xylotriose$. A $\Beta-glucosidase$, also purified from the culture filtrates, hydrolyzed xylan and the neutral or the acidic xylooligosaccharides from the nonreducing end to release only xylose. Neither xylanase nor $\beta-glucosidase$ hydrolyzed the $\beta-(1 → 4)$ linkage between the xylose carrying the branch and the adjacent xylose residue on each side.

Item Type:	Journal Article
Publication:	Archives of Biochemistry and Biophysics
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science
Department/Centre:	Division of Biological Sciences > Biochemistry
Date Deposited:	14 Feb 2008
Last Modified:	19 Sep 2010 04:42
URI:	http://eprints.iisc.ac.in/id/eprint/12791

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