Calcium modulates activity and stability in a novel halotolerant endo-mannanase

Area of Science:

• Biochemistry and Molecular Biology
• Enzymology
• Microbial Biotechnology

Background:

• Mannan, a hemicellulose component, is degraded by beta-mannanases.
• A novel beta-mannanase (Gh_GH26) from the endophytic bacterium Glutamicibacter halophytocola, isolated from a halophilic plant, was identified.
• This enzyme belongs to the glycoside hydrolase 26 family (GH26) and occupies a unique sequence space.

Purpose of the Study:

• To characterize the novel Gh_GH26 enzyme, focusing on its structure, function, and halophilic properties.
• To investigate the role of calcium ions in the activity and stability of Gh_GH26.
• To explore the potential applications of Gh_GH26 in degrading mannan-containing biomass under saline conditions.

Main Methods:

• Bioinformatic analysis of the Gh_GH26 sequence and its domains (including CBM23).
• Enzymatic assays to determine Gh_GH26 activity and halophilic behavior.
• Structural predictions and site-directed mutagenesis to elucidate the role of calcium ions.

Main Results:

• Gh_GH26 exhibits halophilic behavior, retaining activity in high salt concentrations (up to 2.5 M NaCl).
• The enzyme possesses endo-mannanase activity and coordinates Ca2+ ions via its CBM23 domain.
• Calcium ions were found to be essential for both the catalytic activity and stability of Gh_GH26.

Conclusions:

• Gh_GH26 represents a unique member of the GH26 family with significant halophilic properties.
• Calcium ions play a conserved role in modulating enzyme activity and stability, potentially by influencing CBM flexibility.
• This research expands the understanding of GH26 diversity and suggests potential biotechnological applications in saline environments.