Interaction of Polyanions with Basic Proteins, 2

Abstract

The ability of synthetic polyanions to suppress thermo-aggregation of the oligomeric enzymes (glyceraldehyde-3-phosphate dehydrogenase, lactate dehydrogenase, and aspartate aminotransferase) has been established. The ability of the polyanions to reduce the thermo-aggregation increased in the order poly(methacrylic acid) < poly(acrylic acid) < sodium poly(styrene sulphonate), which agreed well with the increase, in the same order, of the charge density of the chains. The lengthening of the chains, as well as the rise in their relative content, resulted in an increase of the ability to reduce thermo-aggregation, mentioned above. Complete prevention of the enzyme aggregation was achieved when highly charged polyanions of a relatively high degree of polymerization were used in a concentration sufficient to solubilize the protein. Complexing with the polyanions prevented thermo-aggregation of the enzymes, but not their thermo-denaturation. The adverse effect of the complexing polyanions on the catalytic activity was reduced by the addition of a synthetic polycation, which resulted in a significant reactivation (up to 40%) of the enzyme. The possibility of preventing the thermo-aggregation of enzyme molecules and then partly restoring the enzyme activity, appears to be of particular interest when studying the aggregation mechanism of proteins that are prone to form the amyloid structures responsible for the development of neurodegenerative diseases like Alzheimer's disease, bovine spongiform encephalopathy and Huntington disease. This finding can also be considered as an important step in the creation of artificial chaperones.

Wrap-and-Strip Technology of Protein–Polyelectrolyte Complex for Biomedical Application

“…This phenomenon is not so surprising because (i) PEG is a kind of aggregation suppressor, (ii) PEG has the salting-out effect, and (iii) a positively charged polyelectrolyte increases the propensity of repulsion between positively charged proteins. Similar phenomena for protein stabilization have been observed for polyanions complexed with basic proteins [48]. The first point is that PEAMA-g-PEG is the aggregation suppressor of proteins.…”

“…The enzyme switch by polyelectrolytes has been indicated by Shalova et al [48]. The paper demonstrated that the heat-treated PPC between glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and anionic polymers of poly(methacrylic acid) and sodium poly(styrene sulfonate) was partially reactivated by addition of strong polycation poly(N-ethyl-4-vinyl pyridinium) bromide.…”

Soluble polyelectrolyte complexes of biopolymers

“…A molecule of the native enzyme consists of four identi cal subunits and may dissociate into dimers or mono mers, depending on the concentration of GADH and the difficulty of denaturation. As was found, the charge density and the polymerization degree of chains charged negatively [25] or positively [26] and their relative content in mixtures with oppositely charged protein, as well as the pH and ionic strength of solutions, may serve as factors for the effective control of thermal aggregation. Thus, when an oppositely charged high molecular mass polyelectrolyte was added to the enzyme solution in an amount sufficient for the solubilization of protein, the thermal aggrega tion of the enzyme was fully suppressed.…”

“…During the use of a relatively hydrophobic polystyrene sulfonate anion, which efficiently suppressed the ther mal aggregation of positively charged GADH mole cules, thermal denaturation proceeded deeply and practically irreversibly [25]. An increase in the hydro phobicity of N alkyl groups of poly(N alkyl 4 vinylpyridinium bromides) enhanced the antiaggrega tion activity of polycations with respect to the nega tively charged GADH but simultaneously facilitated the denaturation of the enzyme [26].…”

“…Recently [25,26], we have used oligomeric enzyme glyceralde hyde 3 phosphate dehydrogenase (GADH), which is inclined to form amyloid structures in vivo, as a model protein to reveal the ability of polyelectrolytes to sup press the thermal aggregation of proteins in vitro. A molecule of the native enzyme consists of four identi cal subunits and may dissociate into dimers or mono mers, depending on the concentration of GADH and the difficulty of denaturation.…”