Stabilization of enzymes

The low content of water in these formulations promotes improved stabilization of enzyme and bleach additives. The combination of LAS and AE in a low-water-content formulation is effective at solubilizing enzymes and preserving enzyme stability when the sum of the LAS and water levels ranges between 25% and 45% [53],... 

Several reports have indicated that enzymes are more thermostable in organic solvents than in water. The high thermal stability of enzymes in organic solvents, especially in hydrophobic ones and at low water content, was attributed to increased conformational rigidity and to the absence of nearly all the covalent reactions causing irreversible thermoinactivation in water [23]. 

Hoare M, Khan MR, DunnUl P (1992) Interfacial damage to proteins during intensive mixing in fermentation and down stream process. In Van Den Tweei WJJ, Harder A, Buitelaar RM (eds) StabUity and stabilization of enzymes, Proc Inter Sym, The Netherland, Elsevier Sci... 

ZAHNLEY J c (1984) Stability of enzyme inhibitors and lectins in foods and the influence of specific binding interactions. Adv Exp Med Biol. 177 333-65. 

Lozano and co-workers reported an interesting stabilization effect of IL for lipase-catalyzed reaction the authors discovered that the presence of an appropriate substrate was essential for stabilization of enzyme in an IL solvent. The half lifetime of native CAL was only 3.2 h in [emim][PFg] solvent, while it lengthened remarkably to 7500 h in the presence of the substrate. The authors succeeded in demonstrating an efficient lipase-recyclable use system based on SCCO2 solvent (Fig. 9). - ... 

Recent other examples of stabilization of enzyme using IL as co-solvent in SCCO2 solvent system Reetz, M. T. Wiesenhofer, W. Francio, G. Leitner, W. Adv. Synth. Catal. 2003, 345, 1221. 

Second, sensors are often intended for a single use, or for usage over periods of one week or less, and enzymes are capable of excellent performance over these time scales, provided that they are maintained in a nfild environment at moderate temperature and with minimal physical stress. Stabilization of enzymes on conducting surfaces over longer periods of time presents a considerable challenge, since enzymes may be subject to denaturation or inactivation. In addition, the need to feed reactants to the biofuel cell means that convection and therefore viscous shear are often present in working fuel cells. Application of shear to a soft material such as a protein-based film can lead to accelerated degradation due to shear stress [Binyamin and Heller, 1999]. However, enzymes on surfaces have been demonstrated to be stable for several months (see below). 

K. Izutsu, S. Yoshioka, and T. Terao, Effect of mannitol crystallinity on the stabilization of enzymes during freeze drying, Chem. Pharm. Bull. (Tokyo), 42, 5 (1994). 

Enzyme electrodes belong to the family of biosensors. These also include systems with tissue sections or immobilized microorganism suspensions playing an analogous role as immobilized enzyme layers in enzyme electrodes. While the stability of enzyme electrode systems is the most difficult problem connected with their practical application, this is still more true with the bacteria and tissue electrodes. 

Bommarius, A.S., Drauz, K., Klenk, H. and Wandrey, C. (1992) Operational stability of enzymes - acylase catalyzed resolution of /V-acetyl amino acids to enantiomerically pure L-amino acids. Annals of the New York Academy of Sciences, 672, 126-136. 

Von der Osten, C. Hedegaard, L 0stergaard, P, Lauridsen, C, Kierstein, L Branner, S. (1993) Stabilization of the detergent protease Savinase by proline substitution in Stability and Stabilization of Enzymes , Van den Tweel, W.J.J., Harder, A Buitelaar, R.M. (eds), Elsevier Science B.V., The Netherlands. 

Asuri P, Karajanagi SS, Vertegel AA, Dordick JS, Kane RS (2007) Enhanced stability of enzymes adsorbed onto nanoparticles. J. Nanosci. Nanotechnol. 7 1675-1678. 

The preceding summary and Fig. 20 present a frame-by-frame account of the pathway for ribonuclease catalysis, based predominandy on knowledge of the structures of the various intermediates and transition states involved. The ability to carry out such a study is dependent on three critical features (1) crystals of the enzyme which diffract sufficiently well to permit structural resolution to at least 2 A (2) compatibility of the enzyme, its crystals, and its catalytic kinetic parameters with cryoenzymology so as to permit the accumulation and stabilization of enzyme-substrate complexes and intermediates at subzero temperatures in fluid cryosolvents with crystalline enzyme and (3) the availability of suitable transition state analogs to mimic the actual transition states which are, of course, inaccessible due to their very short lifetimes. The results from this investigation demonstrate that this approach is feasible and can provide unparalleled information about an enzyme at work. 

High pressure has proven to be a useful tool in biochemistry for the study of a number of cell-mediated processes, the most important being the effect on gene expression. The pressure effect on the stability of enzymes and biopolymers is a topic of general interest that may generate a number of possible applications in the area of food science. Biochemistry and biophysics continue to attract many new research groups, especially in the field of protein chemistry. Pressure may be a tool to obtain unique textures and provide biochemical products with new properties. 

Other noncovalent interactions such as the C=0- -F—C type, between a fluorine atom and the carbonyl of an amino acid, may take place in the stabilization of enzyme-inhibitor supramolecular structures This is why the 4-fluorophenyl group is an important motif for the binding pocket, as shown by the one order-of-magnitude enhancement of the affinity by introducing a fluorine on the thrombin inhibitor (Figure 3.5). "" ... 

Possibility of enhanced stereo selectivity, activity and stability of enzymes... 

A comprehensive description demonstrating the usefulness of protein design to enhance the stability of enzymes can be found (Protein Engineering) in Chapter 7. 

Klibanov, A.M. (1983) Stabilization of enzymes against thermal inactivation. Adv. Appl. Microbiol., 29, 1-28. 

Stellwagen, E (1984) Strategies for increasing the stability of enzymes. Annals N. Y. 

Another important advantage with many non-conventional media is that they can solubilise hydrophobic compounds which are poorly soluble in water. Thereby the conversion of these important substrates is facilitated. Further advantages are that the risk of microbial contamination is much lower in non-conventional media, and under optimized conditions the stability of enzymes is often higher than in aqueous solutions. 

Spectroscopic, that is, fluorescence and circular dichroism (CD), fourier transform infared (FTIR) measurements have been widely applied to analyzing changes in enzyme structures in an attempt to explain the stabilization or denaturation phenomena associated with enzyme environments, for example, temperature, solvents, and so on. All these measurements can also be performed in ILs where fluorescence and CD spectroscopy demonstrated the conformational changes in the native structure of calcium binding proteins (CALB) which resulted in the higher s)mthetic activity and stability in ILs as compared to those obtained in classical organic solvents [18].The stabilization of enzymes by ILs may be related to the associated structural changes of proteins [19]. 

Below, solvent effects on activity and stability of enzymes will be discussed, while solvent effects on enzyme selectivity is a large topic which is treated in a separate chapter. Solvent effects on equilibria are treated in Section 1.4. 

Stability of Enzymes in Nearly Anhydrous Ionic Liquids 235... 

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