Applied Biochemistry and Biotechnology, Vol.169, No.6, 1910-1918, 2013
Heterologous Expression and Characterization of a Glycoside Hydrolase Family 45 endo-beta-1,4-Glucanase from a Symbiotic Protist of the Lower Termite, Reticulitermes speratus
The termite symbiotic system is one of the efficient lignocellulose degradation systems. We tried to express and characterize a novel cellulolytic enzyme from this system. Here, we report the isolation of an endo-beta-1,4-glucanase gene homolog of glycoside hydrolase family 45 from a symbiotic protistan community of Reticulitermes speratus. Heterologous expression of this gene was performed using the expression system of Aspergillus oryzae. Analysis of enzymatic properties revealed 786 mu mol/min/mg protein in specific activity, a V (max) of 833.0 units/mg protein, and a K (m) value of 2.58 mg/ml with carboxymethyl cellulose as the substrate. Thin-layer chromatography analysis showed that RsSymEG2 produces cellobiose from cellodextrins larger than cellohexaose. This enzyme showed high specific activity like other endo-beta-1,4-glucanases from the symbiotic system of termites. It means that the termite symbiotic system is a good resource for highly active endo-beta-1,4-glucanases.