Enzyme-polyelectrolyte complexes in water-ethanol mixtures: Negatively charged groups artificially introduced into α-chymotrypsin provide additional activation and stabilization effects
✍ Scribed by Elena V. Kudryashova; Alexander K. Gladilin; Alexander V. Vakurov; Frederic Heitz; Andrey V. Levashov; Vadim V. Mozhaev
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 282 KB
- Volume
- 55
- Category
- Article
- ISSN
- 0006-3592
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✦ Synopsis
Formation of noncovalent complexes between ␣-chymotrypsin (CT) and a polyelectrolyte, polybrene Biocatalytic systems in homogeneous water-cosolvent (PB), has been shown to produce two major effects on binary mixtures have been the subject of numerous inenzymatic reactions in binary mixtures of polar organic cosolvents with water. (i) At moderate concentrations of vestigations aimed at solving both fundamental and aporganic cosolvents (10% to 30% v/v), enzymatic activity of plied problems, because these media provide a number CT is higher than in aqueous solutions, and this activation of obvious merits (Douzou, 1977; Khmelnitsky et al., effect is more significant for CT in complex with PB (5-1991; Singer, 1962). However, one of the serious disadto 7-fold) than for free enzyme (1.5-to 2.5-fold). (ii) The vantages of these systems is that enzymes are often range of cosolvent concentrations that the enzyme tolerates without complete loss of catalytic activity is much inactivated at comparatively low cosolvent concentrabroader. For enhancement of enzyme stability in the comtions (10% to 40% v/v, depending on enzyme and cosolplex with the polycation, the number of negatively vent) because of denaturation (Khmelnitsky et al., 1991; charged groups in the protein has been artificially in- Mozhaev et al., 1989; Tomiuchi et al., 1993). A number creased by using chemical modification with pyromellitic of approaches directed toward better adaptation of enand succinic anhydrides. Additional activation effect at moderate concentrations of ethanol and enhanced resiszymes to water-cosolvent mixtures have been put fortance of the enzyme toward inactivation at high concenward (Dordick, 1992; Khmelnitsky et al., 1988; Mozhaev trations of the organic solvent have been observed for et al., 1990;Wong, 1992). Formation of noncovalent the modified preparations of CT in the complex with PB enzyme-polyelectrolyte complexes has been suggested as compared with an analogous complex of the native as a new approach to obtain biocatalysts with enhanced enzyme. Structural changes behind alterations in enzyme activity in water-ethanol mixtures have been studied by resistance toward inactivation by organic solvents the method of circular dichroism (CD). Protein conforma- (Gladilin et al., 1995).
tion of all CT preparations has not changed significantly Protein-polycation complexes are spontaneously up to 30% v/v of ethanol where activation effects in enzyformed in aqueous solutions (Izumrudov et al., 1984), matic catalysis were most pronounced. At higher concenmainly due to multiple electrostatic interactions betrations of ethanol, structural changes in the protein have been observed for different forms of CT that were well tween positive charges in polycation and negatively correlated with a decrease in enzymatic activity. © 1997 charged carboxylic groups in the protein molecule.