Hexose-phosphorylating enzyme activities and carbon catabolite control of cellulase formation in Trichoderma reesei QM 9414 and some partially constitutive cellulase producer strains

Dog R mutants of Trichoderma reesei QM 9414, which are able to grow on cellobiose in the presence of 2-desoxyglucose, have been isolated. One of these mutants ( dogR 6) produced cellobiohydrolase I (quantified by ELISA) and carboxymethyl-cellulase not only upon growth on cellulose but also during growth on glucose as a carbon source, and thus was considered to be carbon catabolite derepressed. This mutant and the parent strain were compared with respect to growth and in vivo sugar uptake, and—in view of the role of hexo- or glucokinase in carbon catabolite repression in Saccharomyces cerevisiae and Penicillium chrysogenum, respectively—for formation of hexo- and glucokinase activities during cultivation on a repressing and derepressing carbon source (glucose and lactose, respectively). DogR 6 exhibited strongly retarded growth and sugar uptake. Highest activities of both hexo- and glucokinase were detected during the fast growth phase and were significantly higher on lactose than on glucose. Hexokinase activity of dogR 6 was generally enhanced. However, both activities were clearly higher on lactose than on glucose. Three other T. reesei mutants, which are carbon catabolite derepressed (F4, F5) or insensitive (RUT C-30), were also examined for their hexo- and glucokinase activities. The activities of both enzymes closely resembled those of the catabolite repressible strain QM 9414. From these results, we conclude that the metabolic basis of carbon catabolite insensitive cellulase formation of the T. reesei mutants is not related to a change in their hexose phosphorylating enzyme activities.