Structural and functional analyses of the lipase CinB from Enterobacter asburiae

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• Lipases are crucial enzymes catalyzing ester bond cleavage, found across diverse organisms.
• Enterobacter asburiae lipase CinB (EaCinB) is an acetyl esterase belonging to the α/β-hydrolase superfamily, but its molecular functions remain uncharacterized.

Purpose of the Study:

• To determine the crystal structure of EaCinB.
• To elucidate the molecular function and active site characteristics of EaCinB.
• To investigate the impact of specific mutations on EaCinB's catalytic activity.

Main Methods:

• X-ray crystallography was employed to obtain the high-resolution (1.45 Å) crystal structure of EaCinB.
• Bioinformatic analysis of the primary amino acid sequence.
• Site-directed mutagenesis was performed to create and analyze enzyme variants.

Main Results:

• The crystal structure revealed EaCinB possesses a signal peptide, cap domain, and catalytic domain.
• The active site features a catalytic triad (Ser180-His307-Asp277) and an oxyanion hole (Gly106-Gly107).
• The EaCinB-W208H mutant demonstrated a nine-fold increase in catalytic ability compared to the wild-type (EaCinB-WT).

Conclusions:

• The determined crystal structure provides a molecular basis for understanding EaCinB's function.
• The active site architecture and substrate accessibility are defined.
• Targeted mutagenesis can significantly enhance lipase catalytic efficiency, offering potential for enzyme engineering.