Enzyme-catalyzed reactions in organic

Ideally, thermodynamic activities of the reactants should be used in the equation, but since concentrations are normally easier to measure these are often used instead. The use of the activity of water (which can be measured fairly easily) and the concentrations of the other reactants has been recommended for studies of enzyme catalyzed reactions in organic media (Hailing, 1984). In order to increase the synthesis of the ester, the water concentration (or activity) should be reduced. This can be achieved by replacing part of the water with a water miscible solvent. 

Figure 2.1 Enantioselectivity of enzyme-catalyzed reactions in organic media plotted as a function of the logP-value of the solvent. Data obtained from the literature 1. (open circles) [81], 2. (open diamonds) [17], 3. (closed triangles) [19], 4. (closed circles) [20], 5. (open squares) [82], 6. (closed squares)...

N. J. Turner, Recent advances in the use of enzyme-catalyzed reactions in organic synthesis, Nat. Prod. Rep, 6 625 (1989). 

Guagliardi A, Rossi M, and Bartolucci S. Enzyme-catalyzed Reactions in Organic Solvents. Chimicaoggi 1989 May, 31-36. 

Ayyagari, M.S., Marx, K.A., Tripathy, S.K., Akkara, ).A., and Kaplan, D.L. (1995) Controlled free-radical polymerization of phenol derivatives by enzyme-catalyzed reactions in organic solvents. Macromolecules, 28 (15), 5192-5197. 

S.Butt and S.M.Roberts, Recent Advances in the use of Enzyme-catalyzed Reactions in Organic Research The Synthesis of Biologically Active Natural Products and Analogues, Nat.Prod.Rep., 1986, 3, 489. 

OPTICAL PROPERTIES OF POLYANIUNE SYNTHESIZED BY ENZYME-CATALYZED REACTIONS IN ORGANIC SOLVENTS... 

The use of a lipase to carry out ester syndiesis is one of the earliest examples of enzyme-catalyzed reactions in organic media (1). A voluminous amount of papers has been published in the literature, iiKluding several reviews and books (2). In the polymer and biomaterials areas, lipases and esterases are... 

U Bolz, K Stephan, P Stylos, A Riek, M Rizzi, M Reuss. Comparison of enzymic catalyzed reactions in organic solvents and in supercritical fluids. Biochem Eng —Stuttgart, [Proc. Int. Symp.], 2nd Meeting Date 1990, 82-5. Edited by Reuss, Matthias. Fischer Stuttgart, Fed. Rep. Ger., 1991. 

For desymmetrization of diesters 3 via their hydrolysis in water, pig Hver esterase [12], o -chymotrypsin [12, 13a], and Candida antarctica Hpase (CAL-B) [14] were successfully used. However, further studies showed that respective anhydrides 5 can be used as substrates for enzyme-catalyzed desymmetrization in organic solvents [15]. The desired monoesters 4 were obtained in high yield in this way, using immobilized enzymes Novozym 435 or Chirazyme L-2 (Scheme 5.3). After the reaction, enzymes were filtered off, organic solvents were evaporated, and the crude products were crystalHzed. This was a much simpler experimental procedure in which control of the reaction progress was not necessary, and aU problems associated with extraction of products from aqueous phase and their further purification were omitted [15]. 

Monooxygenase enzymes catalyze reactions in which one atom of oxygen derived from dioxygen is incorporated into an organic substrate while the other atom is reduced by two electrons to form water (1,2). 

Figure 2.2 Enantioselectivity of enzyme-catalyzed reactions in a set of organic media. The order and relative separation of the solvents plotted on the abscissa was obtained by assuming a strict correlation between the particular solvent and the E-value for the...

To appreciate how biochemical reactions serve common functions we must examine the organization of biochemical reactions in some detail. Most of the enzyme-catalyzed reactions in living cells are organized into sequences or path-... 

Enzymatic Modification of Lipids. The value of enzymes as biosynthetic agents has been recognized for many years, particularly in the field of lipids. Because of the highly selective mode of action and the ability of specific enzymes to catalyze reactions in organic—aqueous interfaces, enzymes are useful in synthetic organic chemistry. To enhance stability and the rates of reaction, immobilized enzymes are often used. 

The development of enzyme-catalyzed processes in organic solvents makes it possible to perform enzymatic analysis in organic solvents. Earlier work involved the addition of moderate amounts of solvents to improve substrate solubility, but the new trend is to operate in almost water-free conditions. The selection of reaction parameters is important. Thus, it is necessary to optimize the solvent (118,119) as well as the enzyme support (120). The polarity of the solvent is also important the more polar the solvent, the less stable the enzyme (119). Thus, extremely hydrophobic solvents are useful, provided the substrates and products are soluble. The choice of support is governed by its tendency to attract minute amounts of water present in the system. The supports are characterized with regard to their aquaphilicity There is an inverse correlation between aquaphilidty and catalytic activity of the adsorbed enzyme (121). 

Another factor that greatly influences the rates of enzyme-catalyzed reactions in addition to pH is the presence of an inhibitor. The most dramatic consequences of enzyme inhibition are found in living organisms, where the... 

Metabolism I A set of enzyme-catalyzed reactions in a living organism that builds and breaks down organic molecules, producing or consuming energy in the process. 

Metabolism is the sum total of all the enzyme-catalyzed reactions in a living organism. Many of these reactions are organized into pathways. There are two major types of biochemical pathways anabolic and catabolic. 

Thus, the numerator terms are amplitude factors and the denominator polynomial represents the total nutrient processed by the organism. This allows partitioning the nutrient processed into a number of grossly defined pools. The number of pools is determined by the number of the denominator terms. This is entirely analogous to the rational polynomial which describes the steady state rate of an enzyme-catalyzed reaction in which the denominator consists of the enzyme species and the numerator contains amplitude terms. 

Activity, stability, and selectivity of an enzyme are affected considerably by nature of organic solvents as well as free water content in the enzyme-catalyzed reaction in the organie solvents. However, rational criteria for the selection of a proper solvent among vast variety of the organic solvents are very limited so far. Researchers are obliged to resort to empirical approach by examining some kinds of solvent for the enzyme-catalyzed reaction concerned at the present state of art. 

The similarity of the curves of Figs. 2 and 3 to appropriate curves in Fig. 5 suggests that the growth substance may be involved in an enzyme-catalyzed reaction in which it serves as the substrate. The normal strain of the organism manufactures an amount of the substrate such as to permit the reaction to take place at what may be considered a normal rate, 90 or 95 percent of the maximum rate, which corresponds to saturation of the enzyme. As described above, the gain in reaction rate associated with the manufacture of a larger amount of the substrate, with a corre-... 

The prerequisite for implementing MS in biochemical analysis is that the analytes are amenable to ionization using one of the available ion sources (cf. Chapter 2). A vast majority of biochemical processes occur in the condensed phase. Most enzymes are active in aqueous solutions while only a few of them can catalyze reactions in organic solvents (e.g., transesterification catalyzed by lipase [5]). Water-based buffers are not always the optimum solvents for the operation of ion sources. In fact, concentrated buffer solutions - which are often used in biochemical assays - can suppress ionization, and lead to contamination of... 

K. (2011) Miniaturizing biocatalysis enzyme-catalyzed reactions in an aqueous/organic segmented flow capillary microreactor. Adv. 

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