Jp. Xu et al., XYLANASE INDUCTION BY L-SORBOSE IN A FUNGUS, TRICHODERMA-REESEI PC-3-7, Bioscience, biotechnology, and biochemistry, 62(8), 1998, pp. 1555-1559
Xylanase induction by L-sorbose was studied in a resting cell system o
f a filamentous fungus, Trichoderma reesei PC-3-7, a hypercellulolytic
mutant, and compared with that by other inducers. L-Sorbose induced x
ylanase activity as well as cellulase. It induced a higher level of xy
lanase activity than sophorose and xylose did. Three main xylanases, x
ylanase I (Xyn I), xylanase II (Xyn II), and a non-specific endoglucan
ase I (EG I), were separated using cation-exchange chromatography, and
their activity were measured. Xyn II was induced in about the same pr
oportion (60-80% of the total xylanase activity) by all inducers used.
On the other hand, Xyn I was apparently induced by L-sorbose, xylose,
and xylooligosaccharides, but only a little by sophorose. Northern bl
ot analysis showed that L-sorbose induced Xyn I and Xyn II at the tran
scriptional level, and more xyn1 mRNA was transcribed after L-sorbose
addition than after sophorose. These results suggested that the expres
sions of both Xyn I and Xyn II are regulated, at least in part, in a d
ifferent manner. Furthermore, the Xyn I induction by L-sorbose indicat
ed that an unknown common regulatory mechanism may exist between Xyn I
and cellulase inductions.