scholarly journals Kinetic studies of bovine liver carbamoyl phosphate synthetase

1974 ◽  
Vol 141 (3) ◽  
pp. 807-816 ◽  
Author(s):  
Keith R. F. Elliott ◽  
Keith F. Tipton
Keyword(s):  
Initial Rate ◽  
Kinetic Studies ◽  
Bovine Liver ◽  
Kinetic Mechanism ◽  
Rate Equations ◽  
British Library ◽  
Rate Data ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Lending Library

A through study of initial-rate data has been made on carbamoyl phosphate synthetase from bovine liver. On the basis of the results the order of substrate binding to the enzyme is ATPMg followed by HCO3−, ATPMg and NH4+. A model for the enzymic mechanism is proposed, and the rate equations describing it are presented. Details of the derivation of the initial-rate equation for the kinetic mechanism proposed have been deposited as Supplementary Publication SUP 50032 (6 pages) at the British Library, Lending Division (formerly the National Lending Library for Science and Technology), Boston Spa, Yorks. LS23 7QB, U.K., from whom copies may be obtained on the terms indicated in Biochem. J. (1973), 131, 5.

scholarly journals Product inhibition studies on bovine liver carbamoyl phosphate synthetase

1974 ◽  
Vol 141 (3) ◽  
pp. 817-824 ◽  
Author(s):  
Keith R. F. Elliott ◽  
Keith F. Tipton
Keyword(s):  
Inorganic Phosphate ◽  
Substrate Binding ◽  
Inorganic Ions ◽  
Bovine Liver ◽  
Product Inhibition ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Product Release ◽  
Proposed Model ◽  
Inhibition Studies

A study of the product-inhibition patterns of carbamoyl phosphate synthetase from bovine liver is reported. Inhibition by adenosine, AMP and inorganic ions is also reported. The results are in agreement with the previously proposed model in which the order of substrate binding is ATPMg, followed by HCO3−, ATPMg and NH4+. The order of product release on the basis of the reported results is carbamoyl phosphate, followed by ADPMg, ADPMg and inorganic phosphate.

Succinyl Coenzyme A Synthetase of Escherichia coli: Initial Rate Kinetics of Succinyl-CoA Cleavage and Isotope Exchange Studies

1973 ◽  
Vol 51 (1) ◽  
pp. 44-55 ◽  
Author(s):  
Frank J. Moffet ◽  
W. A. Bridger
Keyword(s):  
Isotope Exchange ◽  
Coenzyme A ◽  
Initial Rate ◽  
Substrate Inhibition ◽  
Kinetic Studies ◽  
Kinetic Mechanism ◽  
Constant Ratio ◽  
Rate Kinetics ◽  
Kinetics Of ◽  
Succinyl Coenzyme A Synthetase

Initial rate kinetic studies of succinyl coenzyme A synthetase of E. coli in the direction of succinyl-CoA cleavage are consistent with the operation of a partially random sequential kinetic mechanism with initial binding of ADP followed by random association of succinyl-CoA and Pi. The mechanism is analogous to that proposed previously for the succinyl-CoA formation reaction, and thus the kinetic mechanism of the overall reversible succinyl-CoA synthetase reaction appears to be symmetrical.Studies of the kinetics of [Formula: see text] isotope exchange at equilibrium show that this partially random sequential kinetic mechanism is not an exclusive pathway. [Formula: see text] isotope exchange rates did not show complete substrate inhibition when CoA or succinate was varied in constant ratio with Pi. However, when CoA or succinate was varied in constant ratio with succinyl-CoA, nearly complete substrate inhibition was observed. These results can be interpreted in terms of a wide variety of minor pathways of substrate binding and product release available to the enzyme under various conditions.

scholarly journals Initial-rate studies of a thermophilic glucokinase from Bacillus stearothermophilus

1987 ◽  
Vol 248 (1) ◽  
pp. 13-20 ◽  
Author(s):  
H Ishikawa ◽  
T Maeda ◽  
H Hikita
Keyword(s):  
Thermal Stability ◽  
Ternary Complex ◽  
Bacillus Stearothermophilus ◽  
Initial Rate ◽  
Rate Equations ◽  
Rate Data ◽  
Michaelis Constant ◽  
Wide Range ◽  
State Assumption ◽  
Reaction Schemes

The initial rates of phosphorylation of glucose catalysed by glucokinase from Bacillus stearothermophilus were measured over a wide range of glucose, MgATP2-, MgADP- and glucose 6-phosphate concentrations. The results of the effects of the inhibitors on the initial rates suggest that the reaction mechanism is essentially the ordered Bi Bi, in which glucose adds to the enzyme before MgATP2- and glucose 6-phosphate is released from the enzyme after the dissociation of MgADP-, and also suggest that the final step in which glucose 6-phosphate is released is irreversible. For many reaction schemes, the rate equations were derived on the basis of the pseudo-steady-state assumption and were used to correlate the experimental rate data. From this result, we concluded that the reaction obeys the ordered mechanism accompanied by the formation of a non-productive ternary complex, glucose-MgADP--enzyme. By using the experimental Dalziel coefficients phi i, some kinetic parameters were evaluated. The enzyme was characterized by the thermal stability and the low Michaelis constant, the values of which were 54 microM for glucose and 32 microM for MgATP2-.

scholarly journals Kinetic studies of dogfish liver glutamate dehydrogenase

1979 ◽  
Vol 177 (2) ◽  
pp. 449-459 ◽  
Author(s):  
A H Electricwala ◽  
F M Dickinson
Keyword(s):  
Glutamate Dehydrogenase ◽  
Kinetic Data ◽  
Reductive Amination ◽  
Initial Rate ◽  
Kinetic Studies ◽  
Bovine Liver ◽  
Binding Studies ◽  
Degree Of Protection ◽  
Binding Sequence ◽  
Kinetic Features

Initial-rate studies were made of the oxidation of L-glutamate by NAD+ and NADP+ catalysed by highly purified preparations of dogfish liver glutamate dehydrogenase. With NAD+ as coenzyme the kinetics show the same features of coenzyme activation as seen with the bovine liver enzyme [Engel & Dalziel (1969) Biochem. J. 115, 621–631]. With NADP+ as coenzyme, initial rates are much slower than with NAD+, and Lineweaver–Burk plots are linear over extended ranges of substrate and coenzyme concentration. Stopped-flow studies with NADP+ as coenzyme give no evidence for the accumulation of significant concentrations of NADPH-containing complexes with the enzyme in the steady state. Protection studies against inactivation by pyridoxal 5′-phosphate indicate that NAD+ and NADP+ give the same degree of protection in the presence of sodium glutarate. The results are used to deduce information about the mechanism of glutamate oxidation by the enzyme. Initial-rate studies of the reductive amination of 2-oxoglutarate by NADH and NADPH catalysed by dogfish liver glutamate dehydrogenase showed that the kinetic features of the reaction are very similar with both coenzymes, but reactions with NADH are much faster. The data show that a number of possible mechanisms for the reaction may be discarded, including the compulsory mechanism (previously proposed for the enzyme) in which the sequence of binding is NAD(P)H, NH4+ and 2-oxoglutarate. The kinetic data suggest either a rapid-equilibrium random mechanism or the compulsory mechanism with the binding sequence NH4+, NAD(P)H, 2-oxoglutarate. However, binding studies and protection studies indicate that coenzyme and 2-oxoglutarate do bind to the free enzyme.

Kinetic mechanism of Escherichia coli carbamoyl-phosphate synthetase

Biochemistry ◽  
1978 ◽  
Vol 17 (26) ◽  
pp. 5587-5591 ◽  
Author(s):  
Frank M. Raushel ◽  
Paul M. Anderson ◽  
Joseph J. Villafranca
Keyword(s):  
Escherichia Coli ◽  
Kinetic Mechanism ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate

scholarly journals The interpretation of kinetic data for enzyme-catalysed reactions involving three substrates

1969 ◽  
Vol 114 (3) ◽  
pp. 547-556 ◽  
Author(s):  
K. Dalziel
Keyword(s):  
Kinetic Data ◽  
Initial Rate ◽  
Rate Equations ◽  
Rate Data ◽  
Designed Experiments

The analysis and interpretation of initial-rate data for reactions involving three substrates, obtained in suitably designed experiments, are discussed. Possible mechanisms for such reactions are classified, the rate equations are compared and the extent to which they can be distinguished experimentally is considered.

scholarly journals Rat liver mitochondrial monoamine oxidase. A change in the reaction mechanism on solubilization

1975 ◽  
Vol 145 (2) ◽  
pp. 311-321 ◽  
Author(s):  
M D Houslay ◽  
K F Tipton
Keyword(s):  
Monoamine Oxidase ◽  
Rat Liver ◽  
Bound State ◽  
Monoamine Oxidase A ◽  
Rate Equations ◽  
British Library ◽  
Ping Pong ◽  
Mitochondrial Monoamine Oxidase ◽  
Lending Library ◽  
Membrane Bound

1. The kinetics of benzylamine oxidation by a soluble preparation of rat liver mitochondrial monoamine oxidase were investigated and were shown to conform to adouble-displacement (or Ping Pong) mechanism. 2. The pathway differs in detail from that followed by other amine oxidases, including the membrane-bound enzyme in rat liver mitochondrial outer membranes. 3. It is suggested taht the conformation of the protein in the soluble state differs from that in the membrane-bound state. 4. The full rate equations for this mechanism have been deposited as Supplementary Publication SUP 50039 (5pages) at the British Library (lending Division) (formely the National Lending Library for Science and Technology), Boston Spa, Yorks, LS237BQ, U.K.. from whom copies can be obtained on the terms indicated in Biochem. J (1975) 145,5.

scholarly journals The kinetic mechanism of ox liver glutamate dehydrogenase in the presence of the allosteric effector ADP. The oxidative deamination of L-glutamate

1984 ◽  
Vol 223 (1) ◽  
pp. 161-168 ◽  
Author(s):  
D P Hornby ◽  
M J Aitchison ◽  
P C Engel
Keyword(s):  
Glutamate Dehydrogenase ◽  
Initial Rate ◽  
Potassium Phosphate ◽  
Kinetic Studies ◽  
Kinetic Mechanism ◽  
Major Effect ◽  
Oxidative Deamination ◽  
Allosteric Effector ◽  
Steady State Kinetic ◽  
State Kinetic

In steady-state kinetic studies of ox liver glutamate dehydrogenase in 0.11 M-potassium phosphate buffer, pH7, at 25 degrees C, the concentration of ADP was varied from 0.5 to 1000 microM. Inhibition was observed except when the concentrations of both glutamate and coenzyme were high, when activation was seen. With NAD+ or NADP+ as coenzyme, 200 microM-ADP was sufficient to saturate the enzyme with respect to the major effect of this nucleotide. In the presence of 210 microM-ADP, widely varied concentrations of coenzyme give linear Lineweaver-Burk plots, in marked contrast with results obtained previously for kinetics without ADP. This has allowed evaluation for the reaction with NAD+, NADP+ and acetylpyridine-adenine dinucleotide (315 microM-ADP in the last case) of all four initial rate parameters, i.e. the phi coefficients in the equation: (Formula: see text) where A is coenzyme and B is glutamate. The relative constancy of phi B and of phi AB/phi A with the different coenzymes point to a compulsory-order mechanism with glutamate as the leading substrate. This conclusion, though unexpected, agrees well with various previous observations on the binding of oxidized coenzyme.

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