Role of Endo-l,4-β-glucanases from Neisseria sicca SB in Synergistic Degradation of Cellulose Acetate(Biochemistry & Molecular Biology)

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An enzyme hydrolyzing β-1, 4 bonds in cellulose acetate was purified 10.5-fold to electrophoretic homogeneity from a culture supernatant of Neisseria sicca SB, which assimilate cellulose acetate as the sole carbon and energy source. The enzyme was an endo-1, 4-β-glucanase, to judge from the substrate specificity and hydrolysis products of cellooligosaccharides, we named it endo-1, 4-β-glucanase I (EG I). Its molecular mass was 50 kDa, 9 kDa larger than EG II from this strain, and its isoelectric point was 5.0. Results of N-terminal and inner-peptide sequences of both enzymes, and a similarity search, suggested that EG I contained a carbohydrate-binding module at the N-terminus and that EG II lacked this module. The pH and temperature optima of EG I were 5.0-6.0 and 45℃. It hydrolyzed water-soluble cellulose acetate (degree of substitution, 0.88) and carboxymethyl cellulose. The K_m and V_<max> for these compounds were 0.296% and 1.29 μmol min^<-1>mg^<-1>, and 0.448% and 13.6 μmol min^<-1> mg^<-1>, respectively. Both glucanases and cellulose acetate esterase from this strain degraded water-insoluble cellulose acetate synergistically.
2003-02-23