Biocatalysis amidases

Some of the industrial biocatalysts are nitrile hydralase (Nitto Chemicals), which has a productivity of 50 g acrylamide per litre per hour penicillin G amidase (Smith Kline Beechem and others), which has a productivity of 1 - 2 tonnes 6-APA per kg of the immobilized enzyme glucose isomerase (Novo Nordisk, etc.), which has a productivity of 20 tonnes of high fmctose syrup per kg of immobilized enzyme (Cheetham, 1998). Wandrey et al. (2000) have given an account of industrial biocatalysis past, present, and future. It appears that more than 100 different biotransformations are carried out in industry. In the case of isolated enzymes the cost of enzyme is expected to drop due to an efficient production with genetically engineered microorganisms or higher cells. Rozzell (1999) has discussed myths and realities... 

The nitrile hydrates employed are selective and stop at the amide stage. However, they display no relevant enantioselectivity. The enantioselectivity in the processes is always introduced by an amidase (see for instance Schemes 6.27 and 6.28) in a second hydrolysis step. Overall the syntheses are, remarkably, often purely catalytic and combine chemical catalysis for reductions with biocatalysis for hydrolyses and the introduction of stereoinformation (Scheme 6.38). 

Fischer-Colbrie, G., Herrmaim, M., Henmann, S., Pnolakka, A., Wirth, A., Cavaco-Panlo, A., and Gnebitz, G.M. 2006. Surface modification of polyacrylonitrile with nitrile hydratase and amidase from Agrobacterium tumefaciens. Biocatalysis and Biotransformation, 24 419-25. 

In biocatalysis, hydrolases are the most important class of enzymes for carrying out enzymatic resolutions. Many hydrolases, such as esterases, lipases, epoxide hydrolases, proteases, peptidases, acylases, and amidases, are commercially available a substantial number of them are bulk enzymes [87]. Resting-cell systems, if they are not immobilized, are used in diluted suspensions and could be handled as quasi-homogeneous catalysts. 

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... 

Vejvoda, V., Kaplan, O., Kubac, D., Kfen, V., and Martmkova, L. (2006). Immobilization of fungal nitrilase and bacterial amidase— two enzymes working in accord. Biocatalysis and Biotransformation, 24,414-418. 

Traditional techniques such as physical adsorption and covalent linkage onto solid supports, entrapment in polymer matrices, and microencapsulation have long been used for immobilizing such enzymes as lipases, proteases, hydantoinases, acylases, amidases, oxidases, isomerases, lyases, and transferases [12-18]. Encapsulation and adsorption have also proved their utility in the immobilization of bacterial, fungal, animal, and plant cells [12-21]. However, as biocatalysis applications have grown, so the drawbacks and limitations of traditional approaches have become increasingly evident. The forefront issues now facing bioimmobilization are indicated in Table 1. 

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