Enzymatic reactions reaction classification

For the reason of comparison and the development of new domino processes, we have created a classification of these transformations. As an obvious characteristic, we used the mechanism of the different bond-forming steps. In this classification, we differentiate between cationic, anionic, radical, pericyclic, photochemical, transition metal-catalyzed, oxidative or reductive, and enzymatic reactions. For this type... 

Such an inter-type difference will not be utilized in this book, mainly because it complicates the classification and is not necessary as tbe focus is placed on the substrates and the products. The argument is also valid for enzymatic transformations [12d, 14], where one enzymatic system with one enzyme or different independent enzymatic systems with one or more enzymes may be used. In Nature, as well as in several artificial enzymatic domino reactions, a mixture of different enzymes catalyzing independent cycles is employed. 

Classification can also be based on potential applications (devices, enzymatic reactions, etc ). 

Table 14.4.3.1. Classification of solvents commonly used for enzymatic reactions in organic media. [Adapted, by permission, from T. Yamane, Nippon Nogeikagaku Kaishi, 65,1104(1991)] ...

Many papers have been published about the enzymatic degradation of polyphenols through the action of oxidizing enzymes. Thus, various classifications have been provided for these types of biocatalytic molecules, according to their coenzyme requirements or according to the nature of the oxidizing substrate (the electron acceptor) and the reaction products (Fig. 4.1). 

Tables 13-la and 13-lb list only the most important categories of enzyme classes (E.C. s). Some enzymes that are involved in reactions at phosphorus are hidden in other classes. For example glyceraldehyde-3-phosphate dehydrogenase, which catalyses the oxidative phosphorylation of glyceraldehyde-3-phosphate to 1,3-diphospho-glycerate, is classified under E.C. 1.2.1.12 and 1.2.1.13. Neither the name of the enzyme nor its IUB-classification, gives information about the phosphorylating step. Identifying enzymes potentially useful in synthesis that have been ambiguously classified is difficult for those outside of biochemistry because no complete reference is available connecting enzymatic activity with synthetic applicability.

Within each of the classifications of reaction-rate methods, there are many different methods of display or mathematical manipulation of the data or equations used to calculate the initial concentration of the species being determined. The calculating technique used can have very significant effects on the accuracy of the analysis. For example, the kinetic role of the species being determined in methods employing first-order or enzymatic or other catalyzed reactions has a strong effect on the choice of measurement of the reaction rate. For the simultaneous, in situ, analysis of several components of a mixture, the choice of method is even more critical with respect to accuracy. Both the relative and absolute values of the rate constants, as well as the initial concentrations of the species to be determined, dictate the choice of method. Furthermore, within the mathematical framework of each of these calculation procedures, there are generally optimum or limited times at which rate data should be taken in order to minimize the effects of random and absolute error in measurement. The choice of procedure and optimization of the measurement... 

Products of catabolism are not included in this classification. During the enzymatic breakdown of molecules, information contained in enzymes u expressed, but instead of being manifested in both the reaction and the product, this information is manifested in the reaction only. Since we are considering products, catabolites as such are non-existent with respect to the proposed classification. 

Koch et al. determined total cholesterol, phospholipids, and fatty acids in CSF samples from 216 individuals in order to establish the lipid and apo-lipoprotein levels in Cerebrospinal Fluid (CSF) in a large group of individuals, on the basis of which a classification of CSF lipoproteins was made. The cholesterol and phospholipids are measured enzymatically by fluorometric detection of the reaction products. Earlier work had shown reduced levels of cholesterol, phospholipids, and free fatty acids in Cerebrospinal Fluid (CSF) of Alzheimer disease patients. Urine levels of F2-isoprostanes or their major metabolite were not significantly different between Alzheimer s disease patients and controls. In addition, urine and CSF F2-isoprostane levels in Alzheimer s disease patients did not correlate. These results indicate that plasma and urine F2-isoprostanes and F2-neuroprostanes do not accurately reflect central nervous system levels of these biomarkers and are not reproducibly elevated in body fluids outside of the central nervous system in Alzheimer s disease patients. 

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