scholarly journals The effect of substitution at C-2 of d-glucose 6-phosphate on the rate of dehydrogenation by glucose 6-phosphate dehydrogenase (from yeast and from rat liver)

1973 ◽  
Vol 131 (1) ◽  
pp. 83-89 ◽  
Author(s):  
Eric M. Bessell ◽  
Peter Thomas
Keyword(s):  
Liver Enzyme ◽  
Rat Liver ◽  
Substrate Inhibition ◽  
Competitive Inhibitor ◽  
Ion Transfer ◽  
Hydride Ion ◽  
Hydride Ion Transfer ◽  
Glucose 6 Phosphate Dehydrogenase

1. The deoxyfluoro-d-glucopyranose 6-phosphates are substrates for both yeast and rat liver glucose 6-phosphate dehydrogenase. 2. The Vmax. values (relative to d-glucose 6-phosphate) were determined for a series of d-glucose 6-phosphate derivatives substituted at C-2. The Vmax. values decreased with increasing electronegativity of the C-2 substituent. This is consistent with a mechanism involving hydride-ion transfer. 3. 2-Deoxy-d-arabino-hexose 6-phosphate (2-deoxy-d-glucose 6-phosphate) showed substrate inhibition with the yeast enzyme but not with the rat liver enzyme. 4. 2-Amino-2-deoxy-d-glucose 6-phosphate (d-glucosamine 6-phosphate) was a substrate for the yeast enzyme but a competitive inhibitor for the rat liver enzyme. 5. Lineweaver–Burk plots for the d-glucose 6-phosphate derivatives with yeast glucose 6-phosphate dehydrogenase were biphasic.

scholarly journals Kinetics and Mechanism of the Oxidation of Substituted Benzaldehydes by Oxo(salen)manganese(v) Complexes

1999 ◽  
Vol 23 (8) ◽  
pp. 480-481
Author(s):  
Varsha Bansal ◽  
Pradeep K. Sharma ◽  
Kalyan K. Banerji
Keyword(s):  
Hydrogen Atom ◽  
Hydrogen Atom Transfer ◽  
Kinetics And Mechanism ◽  
Atom Transfer ◽  
Ion Transfer ◽  
Hydride Ion ◽  
Substituted Benzaldehydes ◽  
Hydride Ion Transfer

The oxidation of benzaldehyde by oxo(salen)manganese(v) complexes proceeds via either a hydride-ion transfer or a hydrogen-atom transfer from the aldehyde to the manganese(v) complex.

The dehydrogenation of 1,4-dihydronaphthalene by tetrachloro-p-benzoquinone

1976 ◽  
Vol 54 (14) ◽  
pp. 2261-2265 ◽  
Author(s):  
Z. M. Hashish ◽  
I. M. Hoodless
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Reaction Rate ◽  
Second Order ◽  
Charge Transfer Complexes ◽  
Ion Transfer ◽  
Hydride Ion ◽  
Rate Determining Step ◽  
Hydride Ion Transfer

The dehydrogenation of 1,4-dihydronaphthalene by tetrachloro-p-benzoquinone in phenetole solution has been investigated. The present work does not fully confirm earlier studies which report that the reaction follows second-order kinetics and that the hydride ion transfer is rate determining. In the investigations described in this paper second-order kinetics are only observed in the later stages of the reaction and a 1:1 stoichiometry of the reactants in the process is not obtained. Substitution of tritium in the 1,4-positions of the hydrocarbon appears to not significantly affect the reaction rate. The present results indicate that charge-transfer complexes are formed in the reaction and it is suggested that electron transfer within these complexes could be the rate-determining step in the dehydrogenation.

Kinetics and mechanism of the oxidation of Substituted Benzylamines by Oxo(Salen)Manganese (V) Complexes

2003 ◽  
Vol 2003 (2) ◽  
pp. 56-57 ◽  
Author(s):  
Rashmi Dubey ◽  
László Kótai ◽  
Kalyan K. Banerji
Keyword(s):  
Kinetics And Mechanism ◽  
Ion Transfer ◽  
Hydride Ion ◽  
Hydride Ion Transfer

The oxidation of substituted benzylamines by oxo(salen) Mn(V) complexes, to the corresponding aldimine, proceeds through a hydride ion transfer from the amine to the oxidant.

scholarly journals Glucose-6-phosphate dehydrogenase. Characteristics revealed by the rat liver enzyme structure

1989 ◽  
Vol 186 (3) ◽  
pp. 551-554 ◽  
Author(s):  
Jonathan JEFFERY ◽  
Jane BARROS-SODERLING ◽  
Lynda MURRAY ◽  
Irene WOOD ◽  
Robert HANSEN ◽  
...  
Keyword(s):  
Liver Enzyme ◽  
Rat Liver ◽  
Enzyme Structure ◽  
Glucose 6 Phosphate Dehydrogenase

scholarly journals The kinetic mechanism and properties of the cytoplasmic acetoacetyl-coenzyme A thiolase from rat liver

1974 ◽  
Vol 139 (1) ◽  
pp. 109-121 ◽  
Author(s):  
B. Middleton
Keyword(s):  
Rat Liver ◽  
Substrate Inhibition ◽  
Kinetic Mechanism ◽  
Competitive Inhibitor ◽  
Acetyl Coa ◽  
Keto Form ◽  
Ping Pong ◽  
Substrate Inhibitor ◽  
The Hill ◽  
Covalent Intermediate

1. Cytoplasmic acetoacetyl-CoA thiolase was highly purified in good yield from rat liver extracts. 2. Mg2+ inhibits the rate of acetoacetyl-CoA thiolysis but not the rate of synthesis of acetoacetyl-CoA. Measurement of the velocity of thiolysis at varying Mg2+ but fixed acetoacetyl-CoA concentrations gave evidence that the keto form of acetoacetyl-CoA is the true substrate. 3. Linear reciprocal plots of velocity of acetoacetyl-CoA synthesis against acetyl-CoA concentration in the presence or absence of desulpho-CoA (a competitive inhibitor) indicate that the kinetic mechanism is of the Ping Pong (Cleland, 1963) type involving an acetyl-enzyme covalent intermediate. In the presence of CoA the reciprocal plots are non-linear, becoming second order in acetyl-CoA (the Hill plot shows a slope of 1.7), but here this does not imply co-operative phenomena. 4. In the direction of acetoacetyl-CoA thiolysis CoA is a substrate inhibitor, competing with acetoacetyl-CoA, with a Ki of 67μm. Linear reciprocal plots of initial velocity against concentration of mixtures of acetoacetyl-CoA plus CoA confirmed the Ping Pong mechanism for acetoacetyl-CoA thiolysis. This method of investigation also enabled the determination of all the kinetic constants without complication by substrate inhibition. When saturated with substrate the rate of acetoacetyl-CoA synthesis is 0.055 times the rate of acetoacetyl-CoA thiolysis. 5. Acetoacetyl-CoA thiolase was extremely susceptible to inhibition by an excess of iodoacetamide, but this inhibition was completely abolished after preincubation of the enzyme with a molar excess of acetoacetyl-CoA. This result was in keeping with the existence of an acetyl-enzyme. Acetyl-CoA, in whose presence the overall reaction could proceed, gave poor protection, presumably because of the continuous turnover of acetyl-enzyme in this case. 6. The kinetic mechanism of cytoplasmic thiolase is discussed in terms of its proposed role in steroid biosynthesis.

scholarly journals Kinetics and Mechanism of the Oxidation of Substituted Benzyl Alcohols by Butyltriphenylphosphonium Dichromate

2002 ◽  
Vol 2002 (8) ◽  
pp. 363-365 ◽  
Author(s):  
Archana Goyal ◽  
Seema Kothari ◽  
Kalyan K. Banerji
Keyword(s):  
Kinetics And Mechanism ◽  
Ion Transfer ◽  
Benzyl Alcohols ◽  
Hydride Ion ◽  
Hydride Ion Transfer

The oxidation of substituted benzyl alcohols by butyltriphenylphosphonium dichromate proceeds by a hydride-ion transfer via a diester intermediate.

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