Samsung Advanced Institute of Technology

Abstract

Biocatalytic conversion of CO2 to other chemicals for sustainable energy production from greenhouse gases has been widely examined. However, the conversion efficiency of these methods is low because they require multiple enzymes and exhibit flux imbalances. To ensure efficient communication among intermediates, we created a hybrid protein scaffold by combining cohesin/dockerin and GTPase-binding domain-Src homology 3 domain-PSD95/DlgA/Zo-1 synthetic scaffold systems, and examined the conversion of CO2 to value added chemicals using a multi-enzyme cascade on the hybrid protein scaffold. Protein-scaffold complexes included formate, formaldehyde, and alcohol dehydrogenases. Cascade enzymes with parallel protein scaffolds exhibited 11.4-fold higher methanol productivity than that of non-scaffolded free enzymes. This is because substrate channeling is 11.3-fold more efficient in scaffolded enzymes than that in free enzymes owing to the shorter inter-enzyme distance, as confirmed by stopped-flow spectroscopy and computational studies. An electrochemical reduction assay also showed that the electron transfer rate of scaffolded enzymes was 3.7 s-1, which was 2.8-fold faster than that of non-scaffolded free enzymes, resulting in a 17.6-fold increased faradaic efficiency. This hybrid protein scaffold system could thus be a novel platform for constructing efficient multi-enzyme cascade reactions.

Keywords: CO2 fixation, hybrid protein scaffold, dehydrogenase, substrate channeling