Protein enzyme aggregates

Later articles dealt with further elaboration of ideas on the driving forces which would have led to the formation of higher aggregates from RNA and amino acids. As had been suggested 20 years earlier, these processes could have taken place in rock pores and could have been driven by hydration and dehydration phases (Kuhn and Waser, 1994). The tiny pores in rocks act as minute test tubes, so optimal compositions could have been determined and replicated using many millions of systems. According to this model, none of the synthetic processes taking place would have required the presence of protein enzymes (see also Lahav, 1999). Just as other... 

Brillouet, J. M., Williams, P., Will, F., Mueller, G., and Pellerin, P. (1996). Structural characterization of an apple juice arabinogalactan-protein which aggregates following enzymic dearabinosylation. Carbohydr. Polym. 29, 271-275. 

Oligomers or enzyme aggregates are often more stable than the eonstituent monomers. Based on this idea of protein-protein interaetions, Shami, Rothstein and Ramjeesingh (1989) have proposed a new approaeh to stabilization using antibodies speeifie for the enzyme. 

The 3-pyridinecarboxyaldehyde 58 is highly water soluble, and so the spontaneous cyanide addition to give racemic cyanohydrin cannot be suppressed unless the aqueous pH is lowered below 3.5, which is not tolerated by the enzymes. The only available option is to operate in a 100% organic solvent system. This was recently made possible by the availability of the cross linked enzyme aggregate particles (CLEAs), which can tolerate organic solvents [64]. The individual precipitated protein molecules are chemically bonded to one another through the formation... 

ATP 4- protein r <1, 2, 4, 5> (<5> microtubule-associated protein, enzyme can also phosphorylate human tau [1] <1> phosphorylates r and forms paired helical filament epitopes, r/Kl, K2, K3 and t/4 repeat [6] <2> enzyme can also phosphorylate bovine tau [4] <2> phosphorylates r protein into Alzheimer disease-like forms, resulting in neuronal death [7] <2> 6 isoforms of human r expressed in adult human brain [12] <2> when a / -mediated aggregated r is used as a substrate for TPKII, an 8fold increase in the rate of TPKII-mediated r phosphorylation is observed... 

Entrapment of enzymes and cells has played an important role in developing bioprocesses. Applications of entrapment technology to biosensors and bioanalysis have mainly been focused on udlizadon of cells and, to a smaller extent, on enzymes (24). Combining covalent coupling and entrapment cross-links enzymes and inert protein to form a protein membrane that covers the sensitive part of the electrode dp in bioanalytical applications (25). Entrapping enzyme aggregates is another variadon of this methodology (26). 

The pH of a solution can affect lipase activity in a number of ways. Like all proteins, enzymes have a tertiary stmcture that is sensitive to pH. In general, denaturation of enzymes occurs at extreme low and high pH values. At extremes of pH, the tertiary structure of the protein may be disrupted and the protein denatured. Many proteins aggregate on pH-induced denaturation and this behavior can be observed by visual inspection. If the activity of an enzyme is plotted against the pH, a bell-shaped curve usually results, with either a sharp or broad pH optimum. 

In the latest years there has been a constant increase of the number of simulation studies concerning large molecules or even supermolecular aggregates, e.g. polymers, proteins or fragments of proteins, enzymes, membrane constituents, stimulated by the development of material science and biotechnology. 

Inhibition of peroxidation of unsaturated lipid chains in biomembranes is of particular significance and interest, because uncontrolled oxidation disrupts the protective layer around cells provided by the membranes. Furthermore, radical chain transfer reactions can also initiate damage of associated proteins, enzymes and DNA. The volume of literature is immense and expanding in the field of antioxidants. We will select certain milestones of advances where micelles and lipid bilayers, as mimics of biomembranes, provided media for quantitative studies on the activities of phenolic antioxidants. One of us, L. R. C. Barclay, was fortunate to be able to spend a sabbatical in Dr. Keith Ingold s laboratory in 1979-1980 when we carried out the first controlled initiation of peroxidation in lipid bilayers of egg lecithin and its inhibition by the natural antioxidant a-Toc . A typical example of the early results is shown in Figure 4. The oxidizability of the bilayer membrane was determined in these studies, but we were not aware that phosphatidyl cholines aggregate into reverse micelles in non-protic solvents like chlorobenzene, so this determination was not correct in solution. This was later corrected by detailed kinetic and P NMR studies, which concluded that the oxidizability of a lipid chain in a bilayer is very similar to that in homogeneous solution . ... 

A key issne concerns the treatment of roles a molecular entity can adopt. Rather than performing multiple inheritance from a protein and catalyst class (static multiple inheritance), for example, to derive an enzyme subclass, we instead combine the role object catalysis with the metabolic entity protein through aggregation (dynamic mnltiple inheritance). Thus, the metabolic entity maintains a list of the roles it can assnme along with the context for each role for instance, a protein may assume the role of catalyst for a given instance of a reaction class. In this way, the protein object can adopt differing roles (e.g., catalyst, transporter) in different scenarios. Also, an object can acqnire additional roles easily as they are discovered without having to modify or rebuild its class definition. 

Angular dependence of light scattered from concentrated solutions of the bovine enzyme is characteristic of scattering from a rod-shaped polymer (58,102). Studies of the small-angle X-ray diffraction (106) and viscosity (107) of enzyme solutions as a function of protein concentration have also shown that the enzyme aggregates to form linear polymers. 

The fusion protein exhibited only one tenth of the XR and XDH activity exhibited by the two enzymes when expressed from separate genes. When the fusion protein was co-expressed with the individual XR and XDH enzymes, aggregates composed of the fusion protein and the separate XR and XDH subunits were confirmed by gel chromatography. This construct had specific XR and XDH activities similar to the individually expressed enzymes. Recombinant S. cerevisiae strains harboring the fusion protein aggregate utilized xylose under oxygen-limited conditions in a defined medium and produced less xylitol than a strain expressing the enzymes separately. 

Akbar U, Aschenbrenner CD, Harper MR et al. (2007) Direct solubilization of enzyme aggregates with enhanced activity in nonaqueous media. Biotechnol Bioeng 96(6) 1030-1039 Albetghina L (2000) Protein engineering in industrial biotechnology. CRC Press, Boca Raton 376 pp. ISBN 9057024128... 

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