Developing a highly efficient 4-hydroxyphenylacetate-3-hydroxylase for salvianic acid A synthesis by computer-aided...

Area of Science:

• Biocatalysis
• Enzyme Engineering
• Metabolic Engineering

Background:

• Salvianic acid A (SAA) is a valuable catechol compound with applications in the food and pharmaceutical sectors.
• Efficient biosynthesis of SAA relies on the enzyme 4-hydroxyphenylacetate-3-hydroxylase (4HPA3H).
• Improving 4HPA3H's catalytic activity towards p-hydroxyphenyllactate acid (4HPLA) is key for enhanced SAA production.

Purpose of the Study:

• To engineer the 4HPA3H enzyme for increased catalytic efficiency towards 4HPLA.
• To identify critical modification sites within the enzyme's substrate pocket.
• To provide insights into enzyme engineering for multi-monomer interactions.

Main Methods:

• Computer-aided molecular modification was employed to redesign the enzyme's substrate pocket.
• Site-directed mutagenesis was used to introduce specific amino acid substitutions.
• Molecular dynamics simulations were performed to analyze changes in enzyme flexibility and activity.

Main Results:

• Mutations at sites T398 (substrate loop) and M205 (distal site) in EcHpaB significantly enhanced catalytic efficiency (kcat/Km) towards 4HPLA.
• Specific mutants (M205F, T398S, M205F/T398S) showed 2.51-, 2.07-, and 2.20-fold increases in catalytic efficiency, respectively.
• Reduced flexibility in the substrate pocket loop was correlated with improved enzyme activity.

Conclusions:

• Enzyme engineering strategies targeting distal sites and substrate loops can effectively enhance biocatalytic activity.
• Modified 4HPA3H enzymes lead to improved SAA biosynthetic efficiency.
• The study highlights the potential of engineering multi-monomer enzyme interactions for biocatalysis.