Biocatalysis reactions Subject

The role of biocatalysis in two-phase systems has many parallels with the subject we have covered under extractive reactions. It appears that a two-phase system was originally considered for transformations of water insoluble substances like steroids. Now, a series of treatises are available which teach us that the maximum value of the apparent equilibrium constant for a second-order reaction in a two-phase system can exceed the equilibrium... 

Many reported biotransformations are initially only demonstrated on a very small scale, the substrates or products may be subject to competing reactions if other enzymes are present (this can be a serious issue in whole-cell biocatalysis), or the desired enzyme is insufficiently active or produced in low levels. For many biotransformations a little care and attention is needed in the growth of the microbe to achieve the desired results. Production of a specific enzyme from a microbe can often be increased by growing the cells in the presence of a very small concentration (typically micromolar) of an inducer. The inducer could be a natural enzyme substrate, a substrate mimic or a molecule which is in some way associated with a substrate s availability or role in metabolism. This process is called induction and represents a genetic switch which cells use to respond... 

As evident from the above discussion, ILs have emerged as alternative solvent systems for biocatalysis which has already established with a range of different class of enzymes performing better or at least comparable to conventional orgattic solvents. The added advantages of easy work up procedure, possibility of recycling the solvent and multiple uses of enzymes were also noted. However, the complexity in the nature of ILs has resulted variation in enzyme performance in terms of reaction rate and enantioselectivity. A brief comparative analysis of enzyme activity versus nature of the component of ILs would be helpful for better understanding of the subject and careful selection of ILs for a desired reaction. 

This is the most common application of biocatalysis in organic synthesis and represents the majority of published examples. Enzymes that catalyze acyl transfer reactions of esters and amides are widely distributed in nature and belong to the lipase/esterase and protease/amidase families, respectively. They play key roles in the metabolism of lipids and proteins and the choice of names, lipase versus esterase, is subject to debate. Normally, acyl ttansfer occurs almost exclusively to water, resulting in hydrolysis. This is particularly valuable for amide hydrolysis that normally requires forcing conditions and strong acid or... 

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