Amidases, modification

An alternative two-step biocatalytic route, first developed at Glaxo in the 1970s, utilized a D-amino acid oxidase and an amidase to provide 7-ACA under physiological conditions (Scheme 1.12). This process has since been established in several companies, with minor modifications. In fact, 7-ACA was manufactured by GSK at Ulverston (Cumbria, UK) using both the chemical and biocatalytic processes in parallel for a period of 2 years during which time the environmental benefits of the biocatalytic process were assessed (see Section 1.6). 

Fischer-Colbrie G, Herrmann M, Heumann S et al (2006) Surface modification of polyacrylonitrile with nitrile hydratase and amidase from Agrobacterium tumefaciens. Biocatal Biotrans 24 419-425... 

Plettner E., DeSantis G., Stabile M. and Jones J. B. (1999) Modulation of esterase and amidase activity of subtilisin Bacillus lentus by chemical modification of cysteine mutants. J. Am. Chem. Soc. 121, 4977-4981. 

Very few reports are available for the enzymatic surface modification of synthetic fibers. Peroxidase, lipase, cutinase, nitrilase, nitrile hydratase, amidase, protease, and hydrolase have been reported for the surface modification of synthetic polymers (Table 4.1). 

Nitrilases and amidases belong to the class of hydrolases and nitrile hydratase belongs to the class of lyase. Nitrilases are an important class of nitrilase superfamily that convert nitrile to the corresponding carboxylic acids and ammonia, whereas nitrile hydratase first converts into the corresponding amide and then this amide is transformed by amidase. There are very few reports for the surface modification of PAN and PA for increasing its hydrophilicity using nitrilases, nitrile hydratases, and amidases. 

Surface modification of polyacrylonitrile with nitrile hydratase and amidase from Agrobacterium tumefaciens. Biocatal. 

Clostripain (EC 3.4.22.8) an SH-dependent, liyp-sin-like protease (M, 50,000) with endopeptidase and amidase-esterase activity, isolated from culture filtrates of Clostridium histolyticum. Ihe endopeptidase acivity hydrolyses proteins, while the amidase-esterase activity cleaves synthetic amino acid amides and amino acid esters. It attacks only arginyl and lysyl re-adues, and is therefore used to isolate large peptide fragments without prior chemical modification of the sutetrate. 

In addition to synthetic appHcations, the NHase/amidase cascade can also be used in post-production processes, like enhancing structure and properties of (poly)acryhc fibers. Tauber et al. [43] showed that the NHase and amidase of R. rhodochrous NCIMB 11216 were able to hydrolyze nitrile groups of both granular polyacrylonitriles (PANs) and acrylic fibers. The acrylic fibers became more hydrophihc because of the enzymatic modification, enhancing the adsorption of dyes. 

Amidases play a significant role in both prokaryotes and eukaryotes, functioning in the production of growth regulators such as auxin and biotin in plants [59], in nutrient metabolism, in the degradation of toxic cyanogenic compounds, and finally in posttranslational modification of amino adds and proteins. 

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