IDENTIFICATION OF A PUTATIVE ACTIVE-SITE RESIDUE IN THE EXO-BETA-(1,3)-GLUCANASE OF CANDIDA-ALBICANS

Recombinant exo-beta-(1-3)-glucanase from Candida albicans was express ed in Saccharomyces cerevisiae and purified. The enzyme contains a num ber of short blocks of sequence homology with several genes for cellul ases of the family A glycanases including the conserved sequence motif NEP which has previously been shown to be important in the catalytic function of several cellulases. Site directed mutagenesis of this glut amic acid residue in the 1,3 glucanase (E230D, E230Q) decreased the en zymatic activity 15,000- and 400-fold, respectively. This suggests tha t the E of the NEP participates in catalysis of the exoglucanase and o ther related glycanases.