ARCHITECTURE OF THE YEAST-CELL WALL - THE LINKAGE BETWEEN CHITIN AND BETA(1-]3)-GLUCAN

Citation
R. Kollar et al., ARCHITECTURE OF THE YEAST-CELL WALL - THE LINKAGE BETWEEN CHITIN AND BETA(1-]3)-GLUCAN, The Journal of biological chemistry, 270(3), 1995, pp. 1170-1178
Citations number
25
Categorie Soggetti
Biology
ISSN journal
00219258
Volume
270
Issue
3
Year of publication
1995
Pages
1170 - 1178
Database
ISI
SICI code
0021-9258(1995)270:3<1170:AOTYW->2.0.ZU;2-X
Abstract
To isolate the putative linkage region between chitin and beta(1-->3)- glucan, Saccharomyces cerevisiae cell walls were digested with beta(1- ->3)-endoglucanase and the reducing ends of the enzyme-resistant gluco se chain stubs were labeled by reduction with borotritide, The radioac tive material was further digested with exochitinase to remove the bul k of the chitin, and the Liberated oligosaccharides were fractionated on a sizing column, A single peak (compound I) was found to consist of N-acetylglucosamine, glucose, and glucitol residues in the ratio 1:2: 1, By digestion with beta-N-acetylglucosaminidase and by NMR spectrosc opy, N-acetylglucosamine was identified as the nonreducing terminus, l inked to laminaritriitol by a beta(1-->4) bond, Five additional oligos accharides were recovered, two being analogs of compound I, with 1 or 3 glucose units, respectively; the remaining three were shown to be th e reduced analogs of laminaribiose, laminaritriose, and laminaritetrao se. The presence of N-acetylglucosamine-containing oligosaccharides ar ises from the activity of chitinase in cleaving 2 sugar units sequenti ally in those chains containing an odd number of N-acetylglucosamine r esidues; correspondingly, oligosaccharides containing only glucose and sorbitol derive from even-numbered chitin chains, a result implying t hat chitinase can hydrolyze the linkage between N-acetylglucosamine an d glucose. It is concluded that the terminal reducing residue of a chi tin chain is attached to the nonreducing end of a beta(1-->3)-glucan c hain by a beta(1-->4) linkage. Experiments with appropriate mutants sh owed that synthesis of the chitin combined with glucan is catalyzed by chitin synthetase 3. The timing and possible mechanism of formation o f the chitin-glucan linkage is discussed.