Expression, Characterization and Structure Analysis of a New GH26 Endo-β-1, 4-Mannanase (Man26E) from Enterobacter aerogenes B19

作者：Liu, Huijing; Liu, Jie; Cui, Tangbing^*

来源：Applied Sciences-Basel, 2020, 10(21): 7584.

DOI：10.3390/app10217584

• Enterobacter aerogenes
• Beta-1
• 4-mannanase
• glycoside hydrolase 26
• catalytic domain

beta-mannanase is one of the key enzymes to hydrolyze hemicellulose. At present, most beta-mannanases are not widely applied because of their low enzyme activity and unsuitable enzymatic properties. In this work, a new beta-mannanase from Enterobacter aerogenes was studied, which laid the foundation for its further application. Additionally, we will further perform directed evolution of the enzyme to increase its activity, improve its temperature and pH properties to allow it more applications in industry. A new beta-mannanase (Man26E) from Enterobacter aerogenes was successfully expressed in Escherichia coli. Man26E showed about 40 kDa on SDS-PAGE gel. The SWISS-MODEL program was used to model the tertiary structure of Man26E, which presented a core (alpha/beta)8-barrel catalytic module. Based on the binding pattern of CjMan26 C, Man26E docking Gal1Man4 was investigated. The catalytic region consisted of a surface containing four solvent-exposed aromatic rings, many hydrophilic and charged residues. Man26E displayed the highest activity at pH 6.0 and 55 degrees C, and high acid and alkali stability in a wide pH range (pH 4-10) and thermostability from 40 to 50 degrees C. The enzyme showed the highest activity on locust bean gum, and the K-m and V-max were 7.16 mg mL(-1) and 508 U mg(-1), respectively. This is the second beta-mannanase reported from Enterobacter aerogenes B19. The beta-mannanase displayed high enzyme activity, a relatively high catalytic temperature and a broad range of catalytic pH values. The enzyme catalyzed both polysaccharides and manno-oligosaccharides.