Enzyme/enzymatic processive artificial enzymes

This process was extended to the phosphorylation of various substrates, in particular to the synthesis of ATP from ADP in mixed solvent [5.62a] and in aqueous solution in the presence of Mg2, probably via formation of a ternary catalytic species 83 [5.62b]. The latter abiotic ATP generating system has been coupled to sets of ATP consuming enzymes resulting in the production of NADH by a combined artificial/natural enzymatic process (Fig. 9) [5.63]. 

Production of the artificial low-calorie sweetener aspartame from Z-L-aspartate and D/L-phenylalanine methylester by peptide bond formation with immobilized thermolysin from Bacillus thermoproteolyticus (Tosoh Corp., Ajinomoto, Toyo-Soda, DSM, annual world production approx. 10000 tons). Aspartame is about 200 times as sweet as sucrose, and is used in drinks such as Coca Cola and Pepsi Cola Light. In contrast to the older chemical process, the enzymatic process can - due to the L-selectivity of the enzyme - use the cheaper D/L-phenylalanine methylester instead of the pure L-form. The enzymatic process (Fig. 15) yields a-aspartame exclusively, whereas the chemical route yields a mixture of a-aspartame and bitter-tasting (5-aspartame, thus requiring an additional separation step. 

As mentioned above, rat liver cytosol contains one or more factors that stimulate microsomal iodothyronine deiodinase activity. It has been realized for more than a decade now that the enzymatic deiodination of iodothyronines is a reductive process which is supported by different synthetic and natural SH compounds [48]. Most investigations of the catalytic mechanism of the deiodinase have utilized artificial cofactors such as the dithiol DTT. The results have demonstrated that both ORD and IRD follow ping-pong type reaction kinetics, indicating that the enzyme exists in two alternating forms induced by the reactions with substrate and cofactor [7,8]. 

Native enzymes, which can spatially and chemically recognize substrate molecules, are powerful catalytic systems in many biochemical processes under mild reaction conditions. The preparation of artificial enzymatic catalysts with the capability of molecular recognition capability, by a molecular-imprinting method, which creates cavities with a similar shape and size to the template molecule in polymer matrices has been developed [1-14]. The technique has been mainly established in the field of analytical chemistry - molecular receptors [15-23], chromatographic separations [24-28], fine chemical sensing [29-33]. All of the methods rely on the selective adsorption of target molecules on imprinted adsorption sites. The number of papers reported per year on molecular imprinting is summarized in Fig. 22.1. 

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