Although there have been a long history of studying and using immobilized enzymes, little has been reported regarding the nature of immobilized cofactors. Herein we report that cofactor NAD(H) covalently attached to silica nanoparticles successfully coordinated with particle-immobilized enzymes and enabled multistep biotransformations. Specifically, silica nanoparticle-attached glutamate dehydrogenase (GLDH), lactate dehydrogenase (LDH) and NAD(H) were prepared and applied to catalyze the coupled reactions for production of α-ketoglutarate and lactate with the cofactor regenerated within the reaction cycle. It appeared that particle-particle collision driven by Brownian motion of the nanoparticles provided effective interactions among the catalytic components, and thus realized a dynamic shuttling of the particle-supported cofactor between the two enzymes to keep the reaction cycles continuing. Total turnover numbers (TTNs) as high as 20,000 h-1 were observed for the cofactor. It appeared to us that the use of particle-attached cofactor promises a new biochemical processing strategy for cofactor-dependent biotransformations.
Bibliographical noteFunding Information:
Liu thanks financial support of a postdoctoral fellowship from National Science Foundation of China (NSFC#20060390522). The authors thank supports from NSFC and Chinese Academy of Sciences (NSFC#20576135, #KSCX2-YW-G-019, and #2006AA02Z217 of 863 initiative). Wang acknowledges the support from US National Science Foundation (BES#0348412). The authors thank Ms. Muqing Zheng for assistance in some of the experimental work.
- Cofactor regeneration
- Enzyme immobilization
- Multi-enzyme biotransformation