Environment Enzyme

Nucleophilic substitution is one of a variety of mechanisms by which living systems detoxify halogenated organic compounds introduced into the environment Enzymes that catalyze these reactions are known as haloalkane dehalogenases The hydrolysis of 1 2 dichloroethane to 2 chloroethanol for example is a biological nude ophilic substitution catalyzed by a dehalogenase... 

As a result of the micellar environment, enzymes and proteins acquire novel conformational and/or dynamic properties, which has led to an interesting research perspective from both the biophysical and the biotechnological points of view [173-175], From the comparison of some properties of catalase and horseradish peroxidase solubilized in wa-ter/AOT/n-heptane microemulsions with those in an aqueous solution of AOT it was ascertained that the secondary structure of catalase significantly changes in the presence of an aqueous micellar solution of AOT, whereas in AOT/n-heptane reverse micelles it does not change. On the other hand, AOT has no effect on horseradish peroxidase in aqueous solution, whereas slight changes in the secondary structure of horseradish peroxidase in AOT/n-heptane reverse micelles occur [176],... 

Life originated in an aqueous environment enzyme reactions, cellular and subcellular processes, and so forth have therefore evolved to work in this milieu. Since mammals live in a gaseous environment, how is the aqueous state maintained Membranes accomplish this by internalizing and compartmentalizing body water. 

Usually, activities of enzymes (hydrogenases included) are investigated in solutions with water as the solvent. However, enhancement of enzyme activity is sometimes described for non-aqueous or water-limiting surroundings, particular for hydrophobic (or oily) substrates. Ternary phase systems such as water-in-oil microemulsions are useful tools for investigations in this field. Microemulsions are prepared by dispersion of small amounts of water and surfactant in organic solvents. In these systems, small droplets of water (l-50nm in diameter) are surrounded by a monolayer of surfactant molecules (Fig. 9.15). The water pool inside the so-called reverse micelle represents a combination of properties of aqueous and non-aqueous environments. Enzymes entrapped inside reverse micelles depend in their catalytic activity on the size of the micelle, i.e. the water content of the system (at constant surfactant concentrations). 

Acetonitrile (MeCN) was used as a model solvent to measure the stability of CPO in a solvent environment. Enzyme assays were performed as just described with the addition of MeCN. The experimental problem of salt precipitation was minimized by using citric acid (7.5 M) for pH adjustment and reducing the phosphate buffer concentration to lOmM. The concentration of the remaining reagents in the CPO assay remained the same. 

Enzymes have an almost mythological reputation for infallible specificity. Surely, when acting in their pertinent biological environments enzymes are highly selective. This selectivity is however partly a consequence of substrate concentration and the absence of relevant competition. It has been shown that when working at non-natural conditions enzymes lose absolute specificity, both chiral and otherwise. Nevertheless, the minimal surface approach to enzyme... 

This catalytic flexibility of enzymes is generally denoted as catalytic promiscuity [52-58], which is divided into substrate promiscuity (conversion of a nonnatural substrate), catalytic promiscuity (a nonnatural reaction is catalyzed), and cOTidition promiscuity (catalysis occurring in a nonnatural environment). Enzymes display three major types of selectivities ... 

Involvement of enzyme in the degradation of PLLA has been controversial. Some studies argue in favor of enzymatic degradation, while others consider the nonenzymatic involvement of PLLA hydrolysis in natural environments. Enzymes play a significant role in the degradation of PLLA, although they are not solely responsible for the hydrolysis of PLLA. 

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