A protein cage can be more than a container for an enzyme: it can change which improvements work. In a study published on 18 October 2023, Taotao Feng, Jiaxu Liu, Xiaoyan Zhang and colleagues engineered enzymes inside virus-like particles to improve chiral alcohol synthesis. Their best variant, called M5, achieved 15 times the starting nanoreactor’s turnover frequency for one model reaction.
Making molecules with the right handedness
Chiral molecules have mirror-image forms that cannot be placed exactly on top of each other, like left and right hands. Making predominantly one form is useful when a chemical synthesis requires a particular molecular arrangement.
The team’s system converts ketones into chiral alcohols. A carbonyl reductase, SsCR from the yeast Scheffersomyces stipitis, performs this reduction using the cofactor NADPH. A second enzyme, glucose dehydrogenase from Bacillus megaterium, uses glucose to regenerate NADPH from its oxidised form, NADP⁺. This allows the cofactor to cycle between the two reactions.
The researchers had already demonstrated this pairing inside particles derived from bacteriophage P22 in a 2021 study. The 2023 work asked how to improve the catalyst in that confined environment. The particles act as nanoscale reaction vessels for chemical synthesis.
Engineering the machinery inside
The team changed the enzymes and an internal scaffold protein while leaving the outer coat protein unchanged. Their approach combined random mutation, activity screening and targeted changes at selected positions. An improved variant therefore had to work after expression and assembly into the particle.
The two activities must stay in balance. Improving ketone reduction alone will not necessarily help if regeneration of the cofactor limits the overall reaction. This makes the complete assembly an important target for screening. Original study.
Why the surroundings matter
The same mutations were also introduced into a matching enzyme fusion outside the cage. That free fusion gained only 1.8-fold in turnover frequency, compared with the 15-fold improvement inside the particle. Both comparisons use each system’s own starting version as the baseline. They do not mean the particle was 15 times faster than every free-enzyme alternative.
The supporting information adds an instructive detail: individual activity measurements did not all improve together. For example, some mutations reduced the reductase’s measured catalytic efficiency even as the complete nanoreactor became more productive under the reaction conditions. Choosing an enzyme by one kinetic measurement can therefore miss how it behaves in a coupled system.
Faster does not always mean more selective
M5 improved turnover for seven of the ten tested substrates; one was unchanged and two were slower. Some products also showed reduced preference for one mirror-image form, although the model product retained 99% enantiomeric excess. These outcomes show why activity and selectivity must be checked separately for each intended product. Original study.
The experiments support further development of enzyme nanoreactors, but they do not establish commercial production costs or environmental savings. The assay conditions included DMSO, and producing and purifying the protein particles also requires resources. Any manufacturing comparison would need to account for those inputs, product recovery and catalyst lifetime.
For enzyme engineers, the practical lesson is to test improvements in the surroundings where the catalyst will work. A mutation selected in dilute solution may behave differently inside a crowded protein cage.
Related reading: Enzymit Puts Enzymes to Work Outside Living Cells.
Update note, 23 September 2026: This archived report was revised to identify the enzyme pair and the components that were engineered, explain the performance comparisons, and remove unsupported claims about pharmaceutical, fragrance and environmental benefits. The original publication date has been retained.
References
- Feng, T., Liu, J., Zhang, X., Fan, D. and Bai, Y. (2023). Protein engineering of multi-enzyme virus-like particle nanoreactors for enhanced chiral alcohol synthesis. Nanoscale Advances, 5, 6606–6616. First published 18 October 2023. DOI: 10.1039/D3NA00515A. Supporting information.
- Zhang, Y.-Q., Feng, T.-T., Cao, Y.-F., et al. (2021). Confining Enzyme Clusters in Bacteriophage P22 Enhances Cofactor Recycling and Stereoselectivity for Chiral Alcohol Synthesis. ACS Catalysis, 11, 10487–10493. DOI: 10.1021/acscatal.1c02221.
