Cellulase regulation

Schuster A, Tisch D, Seidl-Seiboth V, Kubicek CP, Schmoll M (2012) Roles of protein kinase A and adenylate cyclase in light-modulated cellulase regulation in Trichoderma reesei. Appl Environ Microbiol 78 2168-2178... 

Three regulators were identified by genetic analysis. The main repressor, KdgR, controls the transcription of pectinase genes, the intracellular catabolic pathway and the secretion machinery. The PecS repressor controls the production of pectate lyases and cellulases, the secretion machinery and the biosynthesis of a blue pigment. PecT acts as a repressor of the production of some pectate lyases. Other proteins are involved in the regulation of pectinase s5mthesis but their role is not well characterized. 

Microbial cellulases, 70 302 Microbial control regulations, for drinking water, 77 804... 

In the treatment of cellulose pulps one essential criterion for a suitable enzyme preparation is that its cellulase activity should be as low as possible, or preferably absent completely. As even extremely low cellulase activities may ruin pulp quality, Trichoderma enzyme preparations are unlikely to be suitable for these applications. Many bacterial and fungal enzymes with low cellulase activity have been shown to be suitable for treatment of pulps 14, 15, 16,17), Regulation of the often synchronous production of cellulolytic and hemicellulolytic enzymes in micro-organisms is not well understood, and is further complicated by substrate cross-specificity of these enzymes. Enzymes with both endoglucanase and xylanase activity have been reported for bacteria 18, 19) and fungi 20, 21, 22), In addition to selection of strain and... 

Bacteria represent a promising source for the production of industrial enzymes. Bacterial cellulases are an especialfy interesting case in point. Many thermophilic bacterial species produce cellulases that are stable and active at high temperature, resistant to proteolytic attack, and stable to mechanical and chemical denaturation. However, cellulase productivities in bacteria are notoriously low compared to other microbial sources. In this paper bacterial enzyme production systems will be discussed with a focus on comparisons of the productivities of known bacterial cellulase producers. In an attempt to draw conclusions concerning the regulation of cellulase synthesis in bacterial systems, a tentative model for regulation in Acidothennus cellulofyticus has been developed. 

Acidothermus cellulolyticus cellulase activity, 334,335/,341,342/ cellulase production parameters, 341,343r cellulase synthesis regulation, model development, 341-346 concentration vs. rate of cellulase synthesis, 344,345/... 

The multiplicity of cellulases is of fundamental interest because of its implications on the basic understanding of cellulose hydrolysis as well as the regulation of cellulase biosynthesis. 

T. reesei is a useful experimental organism for studying regulation of extracellular protein biosynthesis. When grown in a medium in which an exogeneous inducer serves as the major or sole carbon source, T. reesei, synthesizes and secretes a cellololytic enzyme into the medium. Similarly, the extracellular cellulase is produced upon limitation of the carbon source and limitation of the utilization of the carbon source (31). Presently, there appears to be little data in the literature concerning regulation of cellulase biosynthesis. 

Preliminary experiments done in our laboratory showed that antibodies specific for cellobiohydrolase failed to cross react with either purified cellobiase, purified endoglucanase, or crude endoglucanase. These results, together with data reported in the literature, which show that endoglucanase and cellobiohydrolase have different physical structures, indicate that the three cellulases could be transcribed and translated by different genomes. In this context, then, the question arises as to whether cellulase production is regulated by a common regulatory circuit or by different circuits. 

Montenecourt and Eveleigh (37), using a special agar screening technique, have also isolated a cellulase enhanced mutant (NG-14). They suggest, however, that the cellobiohydrolase and the endoglucanase biosynthesis are regulated by different controls. They base this assumption on data for the relative ratios of cellulases obtained from this mutant needed to hydrolyze different substrates. 

The formation of plant cellulases has been found to be closely regulated by different growth hormones, particularly auxin (6,11), steroids (12), or ethylene gas (13). The hormones act in different tissues under different circumstances, and they seldom lead to such high cellulase activity that there is a net decline in total cellulose. Indeed, cellulose biosynthesis usually continues even while partial hydrolysis occurs, and net cellulose deposition often keeps pace with growth under all of these conditions (14). 

Verma, D. P. S. MacLachlan, G. A. Byrne, H. Ewings, D. Regulation and in vitro translation of messenger ribonucleic acid for cellulase from auxintreated pea epicotyls. 

Because of its ability to produce and secrete the complete set of cellulolytic enzymes, thus making it particularly potent in hydrolyzing the cellulose polymer to glucose monomers, the soft-rot fungus Trichoderma, in particular T. reesei has been the focus of cellulase research for decades (8). The preferred substrates used by most researchers for cellulase production are pure celluloses such as Avicel, Solka-floc, and cotton (9). Cellulase production by Trichoderma is controlled by a complex metabolic regulation (10-12). Cellulose acts (indirectly) as an inducer for the production of cellulases. Expression of cellulases is furthermore subject to repres-... 

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