The association reaction of yeast alcohol dehydrogenase with coenzyme is partly diffusion-controlled in solvents of increased viscosity

Hasinoff, Brian B.; Dreher, Richard; Davey, John P.

doi:10.1016/0167-4838(87)90269-x

Cited by 18 publications

(10 citation statements)

References 21 publications

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“…The dependence of elementary kinetic constants on solvent viscosity provides information on the extent to which a reaction is diffusion-controlled [22][23][24]. This strategy was used in studies on AChE-catalysed substrate hydrolysis [25][26][27].…”

Section: Analysis Of Inhibition Kinetics In Media Of Increasing Viscomentioning

confidence: 99%

Effects of viscosity and osmotic stress on the reaction of human butyrylcholinesterase with cresyl saligenin phosphate, a toxicant related to aerotoxic syndrome: kinetic and molecular dynamics studies

Masson

Lushchekina

Schopfer

et al. 2013

Biochemical Journal

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CSP (cresyl saligenin phosphate) is an irreversible inhibitor of human BChE (butyrylcholinesterase) that has been involved in the aerotoxic syndrome. Inhibition under pseudo-first-order conditions is biphasic, reflecting a slow equilibrium between two enzyme states E and E'. The elementary constants for CSP inhibition of wild-type BChE and D70G mutant were determined by studying the dependence of inhibition kinetics on viscosity and osmotic pressure. Glycerol and sucrose were used as viscosogens. Phosphorylation by CSP is sensitive to viscosity and is thus strongly diffusion-controlled (kon≈10⁸ M⁻¹·min⁻¹). Bimolecular rate constants (ki) are about equal to kon values, making CSP one of the fastest inhibitors of BChE. Sucrose caused osmotic stress because it is excluded from the active-site gorge. This depleted the active-site gorge of water. Osmotic activation volumes, determined from the dependence of ki on osmotic pressure, showed that water in the gorge of the D70G mutant is more easily depleted than that in wild-type BChE. This demonstrates the importance of the peripheral site residue Asp⁷⁰ in controlling the active-site gorge hydration. MD simulations provided new evidence for differences in the motion of water within the gorge of wild-type and D70G enzymes. The effect of viscosogens/osmolytes provided information on the slow equilibrium E⇌E', indicating that alteration in hydration of a key catalytic residue shifts the equilibrium towards E'. MD simulations showed that glycerol molecules that substitute for water molecules in the enzyme active-site gorge induce a conformational change in the catalytic triad residue His⁴³⁸, leading to the less reactive form E'.

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Section: Analysis Of Inhibition Kinetics In Media Of Increasing Viscomentioning

confidence: 99%

Effects of viscosity and osmotic stress on the reaction of human butyrylcholinesterase with cresyl saligenin phosphate, a toxicant related to aerotoxic syndrome: kinetic and molecular dynamics studies

Masson

Lushchekina

Schopfer

et al. 2013

Biochemical Journal

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“…The ingestion of solid particles, such as fibre, should elevate the viscosity of digesta in chicken, as in pigs and rats. Considering the effects of the viscosity of digesta on digestive enzyme reactions (Hasinoff et al 1987), nutrient diffusion behaviour (Takahashi & Sakata, 2002), the absorption rate (Jaroni et al 1999) and the mixing of digesta in the lumen (Lentle et al 2002), the viscosity of digesta with particles should help to reveal the processes involved in digestion and absorption.…”

Section: Relationship Between Solid Particles and Viscositymentioning

confidence: 99%

“…The viscosity of the intestinal contents can affect enzymic reactions (Hasinoff et al 1987) and nutrient absorption (Antoon & Kirsch, 1982), and should define the flow behaviour (Cheremisinoff, 1986) in the lumen of the intestine. The viscosity of the gut contents suppresses the absorption of nutrients in the small intestine of poultry (van der Klis et al 1993).…”

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Viscoelastic properties of the small intestinal and caecal contents of the chicken

2004

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We measured the coefficients of viscosity, shear rates and shear stresses of chicken small intestinal and caecal contents, including solid particles, using a tube-flow viscometer. The coefficients of viscosity of chicken small intestinal and caecal contents were correlated negatively with their shear rates, a characteristic typical of non-Newtonian fluids. The coefficient of viscosity of the small intestinal contents was lower than that of the caecal contents at a shear rate of 1 s 21. Chicken caecal contents were more viscous than pig caecal contents. The exponential relationship between shear stress and shear rate showed that chicken small intestinal and caecal contents had an apparent Herschel -Bulkley fluid nature. These results indicate that solid particles, including uric acid crystals, are mainly responsible for the viscosity of the digesta in the chicken.Broiler: Intestinal contents: Viscoelasticity: Flow behaviour

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“…The sensitivity of this kinetic parameter to viscosity was calculated from the exponential of such plot. The possible non-Stokesian behaviour of Cl − , a small molecule and a product of GST reaction, in the viscosogen/water mixtures were accounted for by exponential of 0.5 [38] , [24] . The second order rate constant ( k cat/ K M ) values decrease with increasing viscosity.…”

Section: Resultsmentioning

confidence: 99%

Catalysis of Silver catfish Major Hepatic Glutathione Transferase proceeds via rapid equilibrium sequential random Mechanism

Kolawole

2016

Toxicology Reports

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Fish hepatic glutathione transferases are connected with the elimination of intracellular pollutants and detoxification of organic micro-pollutants in their aquatic ecosystem. The two-substrate steady state kinetic mechanism of Silver catfish (Synodontis eupterus) major hepatic glutathione transferases purified to apparent homogeneity was explored. The enzyme was dimeric enzyme with a monomeric size of 25.6 kDa. Initial-velocity studies and Product inhibition patterns by methyl glutathione and chloride with respect to GSH-CDNB; GSH-ρ-nitrophenylacetate; and GSH-Ethacrynic acid all conforms to a rapid equilibrium sequential random Bi Bi kinetic mechanism rather than steady state sequential random Bi Bi kinetic. α was 2.96 ± 0.35 for the model. The pH profile of Vmax/KM (with saturating 1-chloro-2,4-dinitrobenzene and variable GSH concentrations) showed apparent pKa value of 6.88 and 9.86. Inhibition studies as a function of inhibitor concentration show that the enzyme is a homodimer and near neutral GST. The enzyme poorly conjugates 4-hydroxylnonenal and cumene hydroperoxide and may not be involved in oxidative stress protection. The seGST is unique and overwhelmingly shows characteristics similar to those of homodimeric class Pi GSTs, as was indicated by its kinetic mechanism, substrate specificity and inhibition studies. The rate- limiting step, probably the product release, of the reaction is viscosity-dependent and is consequential if macro-viscosogen or micro-viscosogen.

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The association reaction of yeast alcohol dehydrogenase with coenzyme is partly diffusion-controlled in solvents of increased viscosity

Cited by 18 publications

References 21 publications

Effects of viscosity and osmotic stress on the reaction of human butyrylcholinesterase with cresyl saligenin phosphate, a toxicant related to aerotoxic syndrome: kinetic and molecular dynamics studies

Effects of viscosity and osmotic stress on the reaction of human butyrylcholinesterase with cresyl saligenin phosphate, a toxicant related to aerotoxic syndrome: kinetic and molecular dynamics studies

Viscoelastic properties of the small intestinal and caecal contents of the chicken

Catalysis of Silver catfish Major Hepatic Glutathione Transferase proceeds via rapid equilibrium sequential random Mechanism

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