Enzymes categorization systems

Many categorization systems exist for enzymes, and the most commonly encountered method is international Enzyme Commission (EC) numbers (Table 4.2). The first number defines the main type of reaction and ranges from one to six. The later numbers further... 

Almost 3200 different enzymes have been listed and categorized by the International Union of Biochemistry and Molecular Biology in its last report in 1992. An encyclopaedic description of more than 7000 commercially available enzymes can be found in Ref [36]. Table 10.2 collects some industrial enzymes suppliers. Enzymes exhibiting the same catalytic function are known as homologous enzymes and they fall into two classes heteroenzymes and isoenzymes. The first group includes enzymes derived from different sources but which catalyse identical reactions, yet show different chemical and kinetic characteristics. A comprehensive enzyme information system, termed BRENDA, is available via the Internet (http //www.brenda.uni-koeln.de). 

Enzyme reactor systems may be of the continuous flow or the stopped-flow variety. Continuous flow systems are further categorized as open or closed systems. The open system, shown in Figure 4.9, continuously pumps fresh buffer through the injector, reactor and detector, ultimately into a waste reservoir for discarding. This arrangement is preferred for the testing of enzyme reactors, since unreacted substrate, cofactors and the products of the enzymatic reactions will not be reexposed to the column. 

Transgenic E. coli accumulate comparatively low levels of carotenoids " compared to microbial algae, yeasts, and bacteria. Many efforts ° have focused on increasing accumulation by manipulation of factors affecting metabolic flux and metabolite accnmnlation (listed and discnssed in Sections 5.3.1.1 and 5.3.1.3 A) and have been reviewed." - " In bacterial systems, approaches to control can be categorized as either infrastructural (plasmids, enzymes, strains) or ultrastructural (media and feeding, enviromnent, precursor pools, substrate flux). 

Apart from specific enzyme systems, the carbon dioxide reduction is mediated by a number of unusual coenzymes that can be categorized into two groups, namely Cj carriers and redox coenzymes [19]. The Cj carriers transport the Cl unit from the substrate carbon dioxide to the end-product methane, while the redox coenzymes provide the electrons that are required for the reduction of carbon dioxide to methane. Members of the first group include methanofuran (MF) (11), tetrahydromethanopterin (H4MPT) (12), and the coenzyme M (CoM-SH) (13), while coenzyme F420 (14) and coenzyme B (CoB-SH) (15) belong to the second group. 

There is also a separate expert system for the combination with MultiCASE, which predicts the possible metabolites, formed of a compound. This system is known as META, which was developed to identify molecular sites susceptible to metabolic transformation. The metabolism dictionary associated with META is able to recognize 663 enzyme-catalyzed reaction rules, which have been categorized into 29 enzyme-reaction classes and 286 spontaneous reactions (Klopman and Rosenkranz 1994). 

While each potential site for non-invasive administration has its own unique features associated with it, some general barriers to delivery do exist. These barriers can be broadly categorized as physicochemical (structural), enzymatic, and cellular (physical). The physicochemical barrier relates specifically to the complex structural properties specific to proteins and peptides. The enzymatic barrier deals with the susceptibility to degrading enzymes associated with a given route of delivery, and the cellular barrier refers to the epithelial membrane that must be crossed for absorption into systemic circulation and includes the related anatomical, histological, and physiological characteristics connected with the site of absorption. 

CYPs are membrane-bound enzymes and are found not only in the kidney and liver, but also the brain, heart, cardiovascular system and the lung, therefore their bioactive products have a myriad of functions in these tissues (Roman 2002). They are categorized according to the clan/family, subfamily, followed by a number. There are 18 mammalian CYP enzyme families, with 41 protein coding subfamilies, and 57 genes that are encoded in the human genome (Roman 2002 Nebert et al. 2013). 

---