The bifunctional fusion protein systems consisting of Rhodococcus erythropolis chiral alcohol dehydrogenase(READH),Candida boidinii formate dehydrogenase(CbFDH) or maltose binding protein(MBP) were constructed to regenerate the cofactors for biocatalysis.READH originated from Rhodococcus erythropolis is an(S)-specific nicotinamide adenine dinucleotide(NADH)-dependent alcohol dehydrogenase,meanwhile,CbFDH originated from Candida boidinii is an NADH-dependent formate dehydrogenase.The strategies of the different fusion protein systems included:(1) fusion of the N terminus of READH to the C terminus of MBP,(2) fusion of the N terminus of CbFDH to the C terminus of MBP,(3) fusion of the N terminus of READH to the C terminus of CbFDH,(4) fusion of the C terminus of READH to the N terminus of CbFDH.The activities of READHs were depressed in all fusion strategies.When the N terminus of READH was fused to the C terminus of CbFDH,READH reached the highest activity,but CbFDH had no activity.In contrast,when the C terminus of READH was fused to the N terminus of CbFDH,CbFDH showed the highest activity,and both moieties displayed activities.From this study,the authors suggest that the rational design of the bifunctional fusion protein system may improve the biocatalysis efficiency by the simultaneous cofactor regeneration.
