A Comparative Reengineering Study of cpADH5 through Iterative and Simultaneous Multisite Saturation Mutagenesis

Area of Science:

• Biotechnology
• Enzyme Engineering
• Directed Evolution

Background:

• Directed evolution utilizes iterative or simultaneous recombination of beneficial mutations.
• Simultaneous site saturation mutagenesis (SSM) offers higher diversity than iterative approaches, crucial for uncovering cooperative effects at proximal residues.
• Candida parapsilosis alcohol dehydrogenase 5 (cpADH5) is a target for enzyme engineering.

Purpose of the Study:

• To comprehensively compare iterative and simultaneous SSM strategies for cpADH5 engineering.
• To identify improved variants of cpADH5 for methyl 3-hydroxyhexanoate conversion.
• To evaluate the efficiency of sequence space coverage in both approaches.

Main Methods:

• Iterative site saturation mutagenesis (SSM) was performed on cpADH5 across 17 recombination paths.
• Simultaneous multisite saturation mutagenesis (OmniChange library) targeted four residues (C57, W116, L119, W286).
• Enzyme activity was screened using methyl 3-hydroxyhexanoate as the substrate.

Main Results:

• Iterative SSM yielded the cpADH5 W286A variant with an 82-fold increase in activity.
• Simultaneous SSM identified the cpADH5 C57V/W286S variant with a 108-fold improvement in activity.
• A 1.8% coverage of the simultaneous SSM sequence space was sufficient to find a superior variant.

Conclusions:

• Simultaneous SSM provides greater enzyme variant diversity compared to iterative recombination.
• Even limited coverage of the simultaneous SSM sequence space can yield significant improvements in enzyme activity.
• This study highlights the advantage of simultaneous SSM for efficient enzyme engineering.