Chemical modulators for enzymatic reactions

In many cases, from the perspective of chemistry, it is difficult to understand the results of enzymatic reactions. For example, it seems strange that only one enantiomer in a racemic compound reacts in an enzymatic reaction if we do not understand the specific interactions between the enzyme and the substrate at the molecular level. The special compositions and structures of biomaeromoleeules endow enzymes with speeial functions. A typical, well-modulated biotransformation is usually considered to be a green process. It is estimated that biocatalysis technologies will decrease consumption of raw materials, water resources, and energy, and reduee waste emissions by 30% in 2020.  

Most enzymatie reactions are performed under mild conditions, such as in water, at room temperature, and at atmospheric pressure, leading to lower energy consumption and operational risks. In addition, it is widely known that enzymes are eapable of catalyzing highly regio-, chemo-, and enantio-selective reactions without performing the lengthy chemical protection/ deprotection steps required in traditional chemical synthesis. 

In spite of the superiority mentioned above, biotransformations are usually not satisfactory in industry without being carefully modulated. One dominant advantage, and sometimes also a drawback, encountered in biotransformations is that enzymatic reactions are traditionally performed in aqueous environments. However, the majority of organic chemicals are water-immiscible, resulting in very low substrate loading and low volumetric productivity. 

In order to enhance the efficiency of biotransformations, chemical modulation can be used, on a case by case basis, to tune the enzyme activity, selectivity, and stability under specific reaction conditions. General methods could be used to improve reaction efficiency, for example, the selection of solvent systems, buffer salts, certain metal ions, and pH adjustments have been reported to work well. The structures and properties of enzymes can be readily regulated in the presence of small-molecule modulators. For example, it is well known that enzymes are able to coordinate with metal ions, which leads to some changes in their properties. In this context, the design and application of chemical modulators in enzymatic reactions is a typical example of chemical biotechnology, as detailed in Chapter 2. 

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