Cloning, heterologous expression and biochemical characterization of a non-specific endoglucanase family 12 from Aspergillus terreus NIH2624

Abstract

The cellulases from Glycoside Hydrolyses family 12 (GH12) play an important role in cellulose degradation and plant cell wall deconstruction being widely used in a number of bioindustrial processes. Aiming to contribute toward better comprehension of these class of the enzymes, here we describe a high-yield secretion of a endoglucanase GH12 from Aspegillus terreus (AtGH12), which was cloned and expressed in Aspergillus nidulans strain A773. The purified protein was used for complete biochemical and functional characterization. The optimal temperature and pH of the enzyme were 55°C and 5.0 respectively, which has high activity against β-glucan and xyloglucan and also is active toward glucomannan and CMC. The enzyme retained activity up to 60°C. AtGH12 is strongly inhibited by Cu²⁺, Fe²⁺, Cd²⁺, Mn²⁺, Ca²⁺, Zn²⁺ and EDTA, whereas K⁺, Tween, Cs⁺, DMSO, Triton X-100 and Mg²⁺ enhanced the enzyme activity. Furthermore, SAXS data reveal that the enzyme has a globular shape and CD analysis demonstrated a prevalence of a β-strand structure corroborating with typical β-sheets fold commonly found for other endoglucanases from GH12 family.

Keywords: Aspergilli; Cellulose; Endoglucanases; GH12; Glycoside hydrolases; Heterologous expression.