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
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.