Polymer-enzyme complex

The stability of the enzyme-polymer complex and its dissociation upon the variation of pH depends on the structural and other physico-chemical properties of CP and enzyme molecule. Thus, a Biocarb-T heteroreticular biosorbent (Fig. 26) is characterized by a stability of its complex with ot-amylase (under the condition of its stabilization) in acid solutions and a complete dissociation of the complex during isolation of the active enzyme at pH 7-8. 

Blinkovsky, A. M., Khmelnitsky, Y. L., and Dordick, J. S., Organosoluble enzyme-polymer complexes a novel type of biocatalyst for nonaqueous media, Biotechnol. 

Vakurov, A. V, Gladilin, A. K., Levashov, A. V, and Khmelmitsky, Y. L., Dry enzyme-polymer complexes stable organosolnble biocatalysts for nonaqneons enzymology, Biotechnol. Lett., 16, 175-178, 1994. 

The enzymatic synthesis of certain polysaccharides is often considered to be by a polyinsertion mechanism. An example of this is the formation of the dextran polyglucoside (see Chapter 31) from saccharose under the influence of the dextran saccharase enzyme. Fructose is eliminated in this reaction. It is assumed that the polymer chain P formed in previous steps is absorbed onto the enzyme. The substrate S (in this case, saccharose) is also absorbed onto the enzyme. A substrate-enzyme complex SEP is formed from the enzyme-polymer complex EP with the substrate S. This is then converted into an enzyme/polymer complex EP +i by insertion of the glucose residue of saccharose with liberation of fructose ... 

Lewis-Acid Catalyzed. Recently, various Lewis acids have been examined as catalyst for the aldol reaction. In the presence of complexes of zinc with aminoesters or aminoalcohols, the dehydration can be avoided and the aldol addition becomes essentially quantitative (Eq. 8.97).245 A microporous coordination polymer obtained by treating anthracene- is (resorcinol) with La(0/Pr)3 possesses catalytic activity for ketone enolization and aldol reactions in pure water at neutral pH.246 The La network is stable against hydrolysis and maintains microporosity and reversible substrate binding that mimicked an enzyme. Zn complexes of proline, lysine, and arginine were found to be efficient catalysts for the aldol addition of p-nitrobenzaldehyde and acetone in an aqueous medium to give quantitative yields and the enantiomeric excesses were up to 56% with 5 mol% of the catalysts at room temperature.247... 

In the authors judgment, catalytic action in the strict sense of the term, implying regeneration of the catalyst, has been rigorously proven in two cases. With other reactions, however, true catalysis has not been unequivocally established. Michaelis-Menten kinetics, indicative of the formation of a substrate-polymer complex, has been shown with each type of reaction. Some of the activities have been very weak, with reaction times for incomplete conversion of substrate measured in days. Others, although not as rapid as enzyme-catalyzed rates, are relatively fast, e.g., the catalytic decarboxylation of OAA by equimolar amounts of lysine residue in polymeric form was over 90% complete in less than 1 hour. 

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