Polymerization, activation regulated

D. Garriga, C. Ferrer-Orta, J. Querol-Audi, B. Oliva and N. Verdaguer, Role of Motif B Loop in Allosteric Regulation of RNA-Dependent RNA Polymerization Activity,/. Mol. Biol, 2013, 425, 2279. 

Regulation Activated by citrate Inhibited by acyl-CoAs In wVo activity regulated bypH.Mg- -. ATP/ADP Activated but not polymerized by citrate Inhibited by (p)ppGpp... 

Because this enzyme catalyzes the committed step in fatty acid biosynthesis, it is carefully regulated. Palmitoyl-CoA, the final product of fatty acid biosynthesis, shifts the equilibrium toward the inactive protomers, whereas citrate, an important allosteric activator of this enzyme, shifts the equilibrium toward the active polymeric form of the enzyme. Acetyl-CoA carboxylase shows the kinetic behavior of a Monod-Wyman-Changeux V-system allosteric enzyme (Chapter 15). 

BFRs are one of the last classes of halogenated compounds that are still being produced worldwide and used in high quantities in many applications. In order to meet fire safety regulations, flame retardants (FRs) are applied to combustible materials such as polymers, plastics, wood, paper, and textiles. Approximately 25% of all FRs contain bromine as the active ingredient. More than 80 different aliphatic, cyclo-aliphatic, aromatic, and polymeric compounds are used as BFRs. BFRs, such as polybrominated biphenyls (PBBs), polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), and tetrabromobisphenol A (TBBPA), have been used in different consumer products in large quantities, and consequently they were detected in the environment, biota, and even in human samples [26, 27]. 

For the last 50 years many scientists have drawn special attention to nitrones due to their successful application as building blocks in the synthesis of various natural and biologically active compounds, of stable nitroxyl radicals, and of other important products for special purposes such as spin traps for the study of radical processes including those that take place in biological systems, and they also found use as both, modifiers and regulators of molecular weight in radical polymerization. 

Brock MA and Chrest F [1993] Differential regulation of actin polymerization following activation of resting T lymphocytes from young and aged mice. J Cellular Phys 157 367-378... 

The U.S. rubber processing industry encompasses a wide variety of production activities ranging from polymerization reactions closely aligned with the chemical processing industry to the extrusion of automotive window sealing strips. The industry is regulated by seven Standard Industrial Classification (SIC) codes [1] ... 

The control via activation or inhibition of the rate(s) of an enzyme-catalyzed reaction(s). This control includes the increase or decrease in the stability or half-life of the enzyme(s). There are many different means by which control can be achieved. These include 1. Substrate availability and reaction conditions (e.g., pH, temperature, ionic strength, lipid interface activation) 2. Magnitude of Vraax sud valucs) 3. Activation (particularly, feedforward activation) 4. Isozyme formation 5. Com-partmentalization and channeling 6. Oligomerization/ polymerization 7. Feedback inhibition and cooperativity (particularly, allosterism and/or hysteresis) 8. Covalent modification and 9. Gene regulation (induction repression)... 

Polymerization and depolymerization of actin, the main component of microfilaments, is controlled by a series of proteins, the activity of which is controlled by Ca and/or Ptdlns(4,5)P2. The Ca regulated proteins (see 6.7) are chiefly involved in processes of depolymerization of actin. Many of the proteins involved in the opposite process, actin polymerization, have specific binding sites for PtdIns(4,5)P2 and Ptlns(4)P and are regulated by the availability of phosphoinositides. Examples of such proteins are profilin, gelsolin, villin and talin (review Janmey, 1994). 

Acetyl-CoA carboxylase is also regulated by covalent modification. Phosphorylation, triggered by the hormones glucagon and epinephrine, inactivates the enzyme and reduces its sensitivity to activation by citrate, thereby slowing fatty acid synthesis. In its active (dephosphorylated) form, acetyl-CoA carboxylase polymerizes into long filaments (Fig. 21-1 lb) phosphorylation is accompanied by dissociation into monomeric subunits and loss of activity. 

Most active principles and pharmaceutical forms are processed in the presence of organic solvents or reagents. The current regulations on products generally restrict to a few p.p.m. the amount of residual solvent. This very low concentration level could favour the CO2 utilization when non-polar compounds have to be eliminated. On the other hand, the elimination of residual solvents from tablets, films or other pharmaceutical preparations in which organic solvent are involved has been addressed [15]. Another application is related to the removal of residues from medical materials such as monomers, additives or polymerization residues from polymers or elastomers. Purification of active principles includes elimination of other undesired molecules pesticides from some vegetal extracts, and antibacterials suspected of toxic co-extracts from natural sources. 

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