Cellulase genes

Cellulase-Negative Xylanase-Positive Mutants. There are two reports concerning the selection of such mutants from filamentous fungi, one on Pofyporus adm-tus (32) and the other cmi Trichoderma reesei (Durand, H. et al. Society CAYLA, Toulouse, France, unpublished results). An analysis of the eliminated cellulase genes has not been done, so it is not known if the mutants negative in endo(l- 4)-p-glucan-ase were deficient also in cellobiohydrolases. 

El-Dorry, H., Crivellaro, O., Leite, A., Abrahao-Neto, J., Enrique-Silva, E, Ascobar-Vera, J., Matheucci, E., Carle-Uriste, J., Pereira, G., Carraro-Pereira, D., and El-Gogary, S. 1996. Transcriptional control of the cellulase genes in Trichoderma reesei. Braz J. Med. Bio. Res., 29, 905-909. 

Ilmen, M., Saloheimo, A., Onnela, M-J., and Penttila, M. 1997. Regulation of cellulase gene expresion in the filamentous fungus Trichoderma reesei. Appl. Environ. Microbiol., 63,1298-1306. 

Penttila, M., Lehtovaara, R, Nevalainen, H., Bhikhabhai, R., and Knowles, J. 1986. Homology between cellulase genes of Trichoderma reesei complete nucleotide sequence of the endoglucanase I gene. Gene, 45, 253-263. 

Figure 3. Illustrations based on AZCL substrates. Three yeast colonies known to contain different cellulase genes were grown for three days on agar plates containing 0.1 % AZCL HE-cellulose (upper) and 0.1 % AZCL xyloglucan (lower). A clear difference in substrate specificity can be observed.

Enzymes acting on molecules like cellulose, which are insoluble and of similar, or even greater size than themselves, obviously require delicate tertiary structures comparison of the sequence of approximately 50 fungal and bacterial cellulase genes and of some other polysaccharide hydrolase (for review see [8]) has offered evidence that such proteins are composed of separate domains, which allow a spacial separation of the sites involved in substrate recognition and enzymatic activity. 

Fig. 1. Domain structure of the four major cellulase genes from T. reesei. Taken from Ref [101], by permission...

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