Structural studies of a cold-adapted dimeric β-D-galactosidase from Paracoccus sp. 32d

Area of Science:

• Enzymology
• Structural Biology
• Biochemistry

Background:

• Cold-adapted enzymes, particularly β-D-galactosidases (GH2 family), are valuable for industrial applications like lactose hydrolysis.
• Previous research focused on tetrameric and hexameric forms, with limited structural data on cold-active dimeric variants.

Purpose of the Study:

• To elucidate the crystal structure of a novel dimeric cold-active β-D-galactosidase (ParβDG) from Paracoccus sp. 32d.
• To understand the structural basis for its dimeric form, catalytic mechanism, and cold-adaptation.

Main Methods:

• Crystal structure determination of ParβDG using molecular replacement with BALBES software at 2.4 Å resolution.
• Determination of the ParβDG-galactose complex structure to identify active site residues.

Main Results:

• The first crystal structure of a functional dimeric cold-active GH2 β-galactosidase was solved.
• The enzyme exhibits a five-domain architecture with the active site near the dimer interface.
• A unique fifth domain (Bgal_windup domain 5) was identified, crucial for dimer stabilization and potentially cold-adaptation.

Conclusions:

• The dimeric structure of ParβDG, particularly the novel domain 5, is key to its stability and function.
• Structural insights into ParβDG provide a basis for engineering cold-active enzymes for biotechnological applications.