A new endoglucanase gene cel124 was cloned from a metagenomic library and expressed in Escherichiacoli. Catalytic triad analysis showed that the catalytic triad sites were different from the known endoglucanases. Cel124, a 34kDa protein, exhibited a specific activity (29.08Umg-1) toward 1% of sodium carboxymethyl cellulose and was stable at 50°C for 30min. The optimal temperature and pH for its catalytic activity were 50°C and pH 5.5 respectively. Cel124 could hydrolyze soluble cellulose, but not insoluble cellulose or other polysaccharides. The kinetic parameters (5.63mgml-1 for Km and 0.0397mmolmin-1mg-1 for Vmax) were measured. 3M NaCl in the system could increase its activity by 2 fold. Site-directe... More
A new endoglucanase gene cel124 was cloned from a metagenomic library and expressed in Escherichiacoli. Catalytic triad analysis showed that the catalytic triad sites were different from the known endoglucanases. Cel124, a 34kDa protein, exhibited a specific activity (29.08Umg-1) toward 1% of sodium carboxymethyl cellulose and was stable at 50°C for 30min. The optimal temperature and pH for its catalytic activity were 50°C and pH 5.5 respectively. Cel124 could hydrolyze soluble cellulose, but not insoluble cellulose or other polysaccharides. The kinetic parameters (5.63mgml-1 for Km and 0.0397mmolmin-1mg-1 for Vmax) were measured. 3M NaCl in the system could increase its activity by 2 fold. Site-directed mutation and circular dichroism spectra test suggested that the residue (Glu41) was essential for its activity, might be a potential active site. Based on our data, we proposed that Cel124 might represent a new type of endoglucanase.
