Joint X ‐ray crystallographic and molecular dynamics study of cellobiohydrolase I from T richoderma harzianum : deciphering the structural features of cellobiohydrolase catalytic activity

Aiming to contribute toward the characterization of new, biotechnologically relevant cellulolytic enzymes, we report here the first crystal structure of the catalytic core domain of C el7A (cellobiohydrolase I) from the filamentous fungus T richoderma harzianum IOC 3844. Our structural studies and molecular dynamics simulations show that the flexibility of T yr260, in comparison with T yr247 from the homologous T richoderma reesei C el7A, is enhanced as a result of the short side‐chains of adjacent V al216 and A la384 residues and creates an additional gap at the side face of the catalytic tunnel. T . harzianum cellobiohydrolase I also has a shortened loop at the entrance of the cellulose‐binding tunnel, which has been described to interact with the substrate in T . reesei C el7 A . These structural features might explain why T . harzianum C el7 A displays higher k cat and K m values, and lower product inhibition on both glucoside and lactoside substrates, compared with T . reesei C el7 A .