Trehalulose synthase native and carbohydrate complexed structures provide insights into sucrose isomerization

Area of Science:

• Enzymology
• Structural Biology
• Biocatalysis

Background:

• Growing demand for sugar substitutes due to sugar-related diseases.
• Industrial potential for enzymatic synthesis of sucrose isomers (trehalulose, isomaltulose) from sucrose.
• Need for understanding sucrose isomerase specificity for controlled synthesis and minimized side reactions.

Purpose of the Study:

• To elucidate substrate binding modes and specificity-determining sites in trehalulose synthase.
• To gain insights into substrate recognition, processing, and reaction specificities.
• To provide a structural basis for engineering improved sucrose isomerases.

Main Methods:

• Determining high-resolution (1.6-2.2 Å) 3D structures of native and mutant trehalulose synthase complexes.
• Utilizing mutagenesis studies to investigate enzyme function and specificity.
• Analyzing substrate binding interactions and key amino acid residues.

Main Results:

• Revealed an 'aromatic clamp' (Phe256, Phe280) crucial for substrate recognition and specificity control.
• Identified essential residues involved in binding glucosyl and fructosyl moieties.
• Demonstrated that structural insights can guide modifications in enzyme action.

Conclusions:

• Structural and mutagenesis data provide thorough insights into trehalulose synthase mechanisms.
• The aromatic clamp is a key determinant of enzyme specificity.
• This study offers a template for designing novel industrial biocatalysts for sugar isomer synthesis.