Structure and Mechanism of the Azomycin Biosynthetic Enzyme RohQ That Catalyzes a Spontaneous Cyclodehydration

Area of Science:

• Biochemistry
• Enzymology
• Structural Biology

Background:

• RohQ is an enzyme in the azomycin biosynthetic pathway.
• It catalyzes the cyclodehydration reaction to form 2-aminoimidazole.

Purpose of the Study:

• To determine the structure and mechanism of RohQ.
• To identify key active site residues involved in catalysis.
• To understand the role of RohQ in de novo enzyme emergence.

Main Methods:

• X-ray crystallography to determine RohQ structure.
• Biochemical assays to study enzyme kinetics and mechanism.
• Site-directed mutagenesis to probe active site residues.

Main Results:

• The structure of RohQ was elucidated, revealing its dimeric form.
• A bound imidazole molecule helped pinpoint active site residues, including two critical aspartic acid residues.
• Catalysis occurs at the dimeric interface, accelerating intramolecular cyclization by 3 × 10⁴-fold.

Conclusions:

• RohQ utilizes a dimeric interface and specific aspartic acid residues for efficient catalysis.
• This work provides the first structural and mechanistic insights into this unexplored protein family.
• The findings contribute to understanding the evolution of de novo enzymes.