Structural Basis for the Catalysis and Substrate Specificity of a LarA Racemase with a Broad Substrate Spectrum.

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• LarA enzymes are racemases/epimerases that interconvert α-hydroxyacid diastereomers.
• They utilize a nickel-pincer nucleotide (NPN) cofactor for catalysis.
• Understanding substrate binding and recognition is crucial for enzyme engineering.

Purpose of the Study:

• To determine the high-resolution structures of enzyme-substrate complexes for a broad-spectrum LarA enzyme.
• To elucidate the mechanism of substrate binding and recognition by LarA enzymes.
• To identify key residues and structural elements governing substrate specificity.

Main Methods:

• X-ray crystallography to obtain high-resolution structures of enzyme-substrate complexes.
• Structural modeling of other LarA enzymes.
• Biochemical analysis of enzyme-substrate interactions.

Main Results:

• Three high-resolution structures of Isosphaera pallida LarA (IpLarA) in complex with its substrate were determined.
• The substrate binding mode shows optimal orientation for proton-coupled hydride transfer.
• Key residues involved in binding diverse α-hydroxyacids were identified.

Conclusions:

• The study provides a structural basis for the catalytic mechanism and substrate specificity of LarA enzymes.
• This work facilitates the engineering of LarA enzymes for various biotechnological applications.
• The findings offer insights into the broader family of NPN-dependent enzymes.