Biocatalysis redox systems

Within biocatalysis, redox reactions especially are often carried out in biphasic systems using crude cell systems, as the recycling of expensive cofactors is vital. The organic phase, which holds the rather insoluble substrate (and products), can be replaced by a more harmless IL. By this means, baker s yeast was used by Howarth and co-workers for enantioselective reduction of ketones [37]. In a 10 1 mixture of [BMIM][PF6] and water, reactions proceeded for a range of substrates giving yields and selectivities very comparable to those obtained by conventional methods [Eq. (8)]. 

Combinatorial biocatalysis, where redox enzymes are used in mulit-component systems for new molecule discovery. 

The electrons that must be delivered to the heme iron to accomplish catalysis are transferred from the reduced cofactor NAD PH by the redox partners. Nature uses a variety of strategies to accomplish this, almost all of which rely on intermediary electron transfer proteins that themselves require nonprotdnaceous cofactors. There are currendy at least 10 different systems or classes known [15], but for the purposes of applied biocatalysis, it is important to be aware of the four most commonly encountered in the biocatalysis literature (Figure 8.4). 

---