Triggering of cellulase biosynthesis by cellulose in Trichoderma reesei. Involvement of a constitutive, sophorose-inducible, glucose-inhibited beta-diglucoside permease.
We prepared [U-14C]cellobiose by cultivating Acetobacter pasteurianus in the presence of [U-14C]glucose and hydrolyzing the [U-14C]cellulose formed with beta-glucosidase-free cellulase from Trichoderma reesei. This 14C-labeled cellobiose was used to investigate the presence of an uptake system for cellobiose in T. reesei. Evidence was obtained for the presence of a high affinity (Km for cellobiose 0.3 microM) but low activity (2.5 milliunits/mg fungal dry weight) cellobiose permease. The permease is formed constitutively, but higher levels are formed after addition of sophorose (glucosyl-beta-1,2-diglucoside), a reputed cellulase inducer. The permease appears to be specific for beta-diglucosides, as the uptake of [U-14C]cellobiose is inhibited by sophorose, gentiobiose (glucosyl-beta-1,3-glucoside), and cellobiose. Under these conditions, cellooligodextrines (n, 4-7; final concentration, 1 mM) are not inhibitors. Glucose, but no other monosaccharides, inhibits the permease. The hypersecretory mutant T. reesei RUT C-30 exhibits elevated permease activities, whereas in T. reesei QM 9979, a mutant strain defective in the induction of cellulases by cellulose or sophorose, strongly reduced permease activities were demonstrated. The results stress a hitherto not recognized point of control in the induction of cellulases by T. reesei at the level of uptake of cellulose oligosaccharides.
Kubicek
C P
CP
Institut für Biochemische Technologie und Mikrobiologie, Abteilung für Mikrobielle Biochemie, TU Wien, Austria.
Messner
R
R
Gruber
F
F
Mandels
M
M
Kubicek-Pranz
E M
EM
D002480:Cellulase / Q000096:biosynthesis* / Q000302:isolation & purification; D002482:Cellulose / Q000494:pharmacology*; D004790:Enzyme Induction; D005936:Glucans / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology*; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000378:metabolism*; D013045:Species Specificity; D013379:Substrate Specificity; D014242:Trichoderma / Q000201:enzymology*; D001617:beta-Glucosidase / Q000302:isolation & purification / Q000378:metabolism
D005936:Glucans; D026901:Membrane Transport Proteins; D002482:Cellulose; D001617:beta-Glucosidase; D002480:Cellulase; D005947:Glucose; C003328:sophorose