INTRINSIC FLUORESCENCE IN ENDOGLUCANASE AND CELLOBIOHYDROLASE FROM TRICHODERMA-PSEUDOKININGII S-38 - EFFECTS OF PH, QUENCHING AGENTS, AND LIGAND-BINDING

To gain further insight into the difference in substrate specificity b etween endoglucanase and cellobiohydrolase, the intrinsic fluorescence properties of cellobiohydrolase I (CBHI) and endoglucanase I (EG I) f rom Trichoderma pseudokiningii S-38 were investigated. The results for the spectral characteristics, ligand binding and fluorescence quenchi ng suggest that the fluorescence of two enzymes comes from tryptophan residues, and that tryptophan residue(s) may be involved in the functi on of the two enzymes. The results also suggest that the binding trypt ophan in EG I may be more exposed to solvent than that in CBHI. This i nterpretation is supported by the observations that the effects of pH upon the fluorescence of EG I are greater than that of CBHI; spectral shifts are different in EGI and CBHI under various conditions, and flu orescence lifetime changes caused by cellobiose binding are larger for EGI than for CBHI.