Enzymes pressure changes

Data of chemical composition 106 Pressure changes 145 Variables related to composition 164 Half iife and initial rate data 177 Temperature variation. Activation energy Homogeneous catalysis 202 Enzyme and solid catalysis 210 Flow reactor data 222 CSTR data 231 Complex reactions 238... 

Some enzyme-catalysed reactions result in the production or uptake of a gas and some of the earliest assay methods used this phenomenon as a basis for monitoring the reaction. Classically, Krebs, in elucidating the metabolism of glucose, used such methods. They measure either the pressure changes that... 

Although many chemical catalysts can work under various conditions of temperature and pressure as well as alkalinity or acidity, biological catalysts operate only under very particular conditions. For example, they operate over a very narrow temperature range and if the temperature becomes too high, they become inoperative. At temperatures above about 45 °C, they denature. This means that the specific shape of the active site of the enzyme molecule changes due to the breaking of bonds. This means that the reactant molecules are no longer able to fit into the active site. 

Proteins are not very sensitive to pressure changes, and only at large values of pressure do they exhibit conformational changes observed when denatured by heat or changes in solution pH. A model enzyme (protein), namely, urease, did not lose much of its activity until the compaction pressure exceeded 474 mPa, above which 50%i of the relative activity was lost. ... 

Kamat SV, Beckman EJ, Russell AJ. Control of enzyme enantioselectivity with pressure changes in supercritical fluoroform. J Am Chem Soc 1993 115 8845-8846. 

Properties Colorless clear vise, liq. mild odor sol. in most org. soivs., 95% ethanol, acetone, DMSO, ketones, chlorinated hydrocarbons sol. < 1 mg/ml in water insol. in aliphatic hydrocarbons m.w. 430.91 dens. 1.508 g/cm (22.2 C) vapor pressure 10.3 mm Hg (25 C) f.p. 27 C b.p. 236-237 C (5 mm) flash pt. 252 C ref. index 1.5022 Toxicology LD50 (oral, rat) 1850 mg/kg, (skin, rabbit) > 23,700 mg/kg mod. toxic by ing. may cause irritation of skin, respiratory tract cholinesterase inhibitor may cause tremors, convulsions, irritability, hypermotility, diarrhea, enzyme inhibition, change in blood/tissue levels, changes in liver/kidney wt questionable carcinogen experimental teratogen and reproductive effects mutagenic data ... 

Reaction quotient (Q) An expression with the same form as Kbut involving arbitrary rather than equilibrium partial pressures, 333-334 Reaction rate The ratio of the change in concentration of a species divided by the time interval over which the change occurs, 285 catalysis for, 305-307 collision model, 298-300 concentration and, 287-292,314q constant, 288 enzymes, 306-307 egression, 288... 

Substances that do not target the active site but display inhibition by allosteric mechanisms are associated with a lower risk of unwanted interference with related cellular enzymes. Allosteric inhibition of the viral polymerase is employed in the case of HIV-1 nonnucleosidic RT inhibitors (NNRTl, see chapter by Zimmermann et al., this volume) bind outside the RT active site and act by blocking a conformational change of the enzyme essential for catalysis. A potential disadvantage of targeting regions distant from the active site is that these may be subject to a lower selective pressure for sequence conservation than the active site itself, which can lower the threshold for escape of the virus by mutation. 

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