Enzyme-anion exchanger

Bile Acid Sequestrants. The bile acid binding resins, colestipol [26658424] and cholestyramine, ate also effective in controlling semm cholesterol levels (150). Cholestyramine, a polymer having mol wt > ICf, is an anion-exchange resin. It is not absorbed in the gastrointestinal tract, is not affected by digestive enzymes, and is taken orally after being suspended in water (151). 

Figure 6A-C. High-performance anion-exchange chromatography elution profile of isolated modified hairy regions without addition of enzymes (A), with Biopectinase OS (B) and with rhamnogalacturonase-containing culture filtrate from an A. awamori multicopy transformant (C). /xC ftCoulomb- Data taken from Ref. 6.

Figure 15.4(A) shows the effect of the R = Zn2+/Al3+ ratio, which determines the charge density of the LDH layer, on the Freundlich adsorption isotherms. K values are far higher than those measured for smectite or other inorganic matrices. The increase in Kf with the charge density (Kf= 215, 228, 325mg/g, respectively, for R = 4, 3 and 2) is supported by a mechanism of adsorption based on an anion exchange reaction. The desorption isotherms confirm that urease is chemically adsorbed by the LDH surface. The aggregation of the LDH platelets can affect noticeably their adsorption capacity for enzymes and the preparation of LDH adsorbant appears to be a determinant step for the immobilization efficiency. [ZnRAl]-urease hybrid LDH was also prepared by coprecipitation with R = 2, 3 and 4 and Q= urease/ZnRAl from 1 /3 up to 2.5. For Q < 1.0,100 % of the urease is retained by the LDH matrix whatever the R value while for higher Q values an increase in the enzyme/LDH weight ratio leads to a decrease in the percentage of the immobilized amount.

The adsorbent should have a high affinity and capacity for the enzyme and it should not absorb the reaction product or enzyme inhibitors. Among the materials used the more popular are cation and anion exchange resins, activated charcoal, silica gel, alumina, control pore glasses and ceramics. 

The number of enzymes and functional proteins that are reportedly regulated by S-nitrosation is on the rise. For example, a search of PUBMED with the key word S-nitrosation revealed some 70 reports of in vitro regulation of enzymes, proteins and cellular processes that are affected by S-nitrosation. Some of these processes that have been well characterized include, nuclear regulatory proteins the NMDA receptor and the ertrocyte anion exchange protein 1 (AE1) (see review by Gaston, 2003). 

Lignin peroxidases enzymes In-process control, semipreparative purification, comparison with conventional columns Anion Exchange disks [80]... 

The pellet was redissolved in buffer A, dialysed overnight against the same buffer and loaded on an anion-exchange column (Fractogel EMD DEAE, 10 cm x 2 cm) which was previously equilibrated with buffer A. The enzyme was eluted with a linear gradient from 0 to 0.15 m NaCl for 30 min in the same buffer, at a flow rate of 2 mL... 

Selenoprotein A is remarkably heat stable, as seen by the loss of only 20% of activity on boiling at pH 8.0 for lOmin (Thrner and Stadtman 1973). Although selenoprotein A contains one tyrosine and no tryptophan residues, it contains six phenylalanine residues and thus has an unusual absorbance spectrum (Cone et al. 1977). Upon reduction, a unique absorption peak emerges at 238 nm, presumably due to the ionized selenol of selenocysteine, which is not present in the oxidized enzyme. The activity of selenoprotein A was initially measured as its ability to complement fractions B and C for production of acetate from glycine, in the presence of reducing equivalents (e.g., dithiothreitol). Numerous purification schemes were adopted for isolation of selenoprotein A, all of which employed the use of an anion exchange column to exploit the strongly acidic character of the protein. 

Initial Fractionation. The most effective method found for the initial fractionation of the complex enzyme mixtures present in wood-culture extracts was anion exchange chromato phy eluting with salt gradients (9,74,75). This permitted further sample concentration by functioning as a solid phase extractant during loading. It also showed higher sample capacity and better separations than other methods. 

Although effective, residual polyphenols in crude samples resulted in less separation than possible with this method. Such binding often resulted in peaks containing several different activities (9). And increased sample loading often broadened and reduced the number of peaks (9,74). Due to these interferences, two different scales of anion exchange chromatography were used. Analytical separations were used to gather information about the enzymes present and preparative separations were used to purify enzyme quantities sufficient for characterization. 

Figure 2. Enzyme activities in analytical QM anion exchange column fractions detected with substrates selected for cellulases. Major peaks are numbered. (Reproduced with permission from ref. 9. Copyright 1990 Society of Fermentation Technology, Japan.)...

Figure 5. Optical absorbance at 280nm and 409nm (denoting heme-iron containing ligninases) for fractions from the preparative DEAE anion exchange column and salt gradient used to fractionate the enzymes in a crude culture extract. (Reproduced widi permission from ref. 15. Copyright 1990 Springer-Verlag.)...

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