Enzymatic Approaches

For the identification of the C-terminal residue of polypeptides, an enzymatic approach is commonly used. 

Two appendices are included at the end of this chapter. The first is intended to serve as a reminder, for those of you who might need it, of the nomendature and representation of stereoisomers. The second appendix contains descriptions of various chemo-enzymatic methods of amino acid production. This appendix has been constructed largely from the recent primary literature and includes many new advances in the field. It is not necessary for you to consult the appendix to satisfy the learning objectives of the chapter, rather the information is provided to illustrate the extensive range of methodology assodated with chemo-enzymatic approaches to amino add production. It is therefore available for those of you who may wish to extend your knowledge in this area. Where available, data derived from die literature are used to illustrate methods and to discuss economic aspects of large-scale production. 

R. L. Sinsabaugh, R. K. Antibus, and A. E. Linkins, An enzymatic approach to the analysis of microbial activity during plant litter decomposition. Agricult. Ecosyst. Environ.. 14 43 (1991). 

The polyester domains of suberized walls can also be depolymerized using chemical and/or enzymatic approaches similar to those used for cutin. The aromatic domains are far more difficult to depolymerize as C-C and C-O-C crosslinks are probably present in such domains. Therefore, more drastic degradation procedures such as nitrobenzene, CuO oxidation, or thioglycolic... 

A number of modified lactoses were prepared by enzymatic approach (Fig. 63).84... 

DNA can be isotopically labeled not only using the enzymatic approach mentioned above but also using solid-state phosphoamidite synthesis. This methodology, developed in the 1980 s and modified recently to incorporate the isotope labels, is of advantage when residue- and site-specific patterns of 13C and/or 15N and/or 2H labeling is needed [3]. 

Several enzymatic procedures have been developed for the synthesis of carbohydrates from acyclic precursors. Aldolases appear to be useful catalysts for the construction of sugars through asymmeteric C-C bond formation. 2-deoxy-KDO, 2-deoxy-2-fluoro-KDO, 9-0-acetyl sialic acid and several unusual sugars were prepared by a combined chemical and enzymatic approach. Alcohol dehydrogenases and lipases have been used in the preparation of chiral furans, hydroxyaldehydes, and glycerol acetonide which are useful as building blocks in carbohydrate synthesis. 

The enzymatic approach to the synthesis of carbohydrates and their precursors is practical for certain types of sugars. The next stage of our investigation will be to focus on the modification of these readily available sugars to agents of interest. Improvement of enzyme properties for synthetic application is also of interest. 

Chemical and Chemo-Enzymatic Approaches to Glycosidase Inhibitors with Basic Nitrogen in the Sugar Ring... 

Chemical and Oiemo-Enzymatic Approaches to Glycosidase Inhibitors orith Basic Nitrogen... 

Small amounts of farnesylated or geranylgeranylated peptides can be obtained by enzymatic methods, whereby the C-terminal sequence (Table 1) for recognition of the peptides as substrates by the farnesyltransferase and geranygeranyltransferase I is required. This enzymatic approach is particularly useful for the synthesis of [3H]-labeled derivatives. 

It was observed that for CCK and related peptides sulfation of the tyrosine residue is essential for triggering the full hormonal response.131 32 More recently, additional sulfated peptides have been identified as CCK-58, 135 phytosulfokinine-a, as peptide growth factor in plants 136 as well as various toxins from Conus venom. 137138 This observation has fostered intensive research to develop synthetic methods for efficient production of tyrosine O-sulfated peptides by chemical and enzymatic approaches. 

The problem was solved using a more traditional chemo-enzymatic approach in which the sugar amino group was preliminarily protected by reacting 8 with... 

For instance, subtilisin-catalyzed esterification of lactosides has been used for a chemo-enzymatic approach to 6 -deoxy-6 -fluoro- and 6-deoxy-6-fluoro-lactosides... 

Finally, Kren and coworkers have proposed the use of selectively acylated glycosides to be used as acceptors in a bi-enzymatic approach to the synthesis of di- and trisaccharides exploiting lipases/proteases and glycosidases (for instance, 6-0-acetyl-N-acetyl-D-glucosamine, 14, to give the corresponding chitobiose derivative 15) [44]. 

---