Product-Inhibition Studies on Pyruvate Kinase Isolated from the Leg Muscle of Carcinus maenas

1976 ◽  
Vol 4 (4) ◽  
pp. 622-624
Author(s):  
COLIN J. NEWTON ◽  
PETER C. POAT ◽  
KENNETH A. MUNDAY
Keyword(s):  
Pyruvate Kinase ◽  
Carcinus Maenas ◽  
Product Inhibition ◽  
Leg Muscle ◽  
Inhibition Studies

scholarly journals A steady-state kinetic analysis of the fructose 1,6-bisphosphate-activated pyruvate kinase from Carcinus maenas hepatopancreas

1980 ◽  
Vol 185 (2) ◽  
pp. 289-299 ◽  
Author(s):  
I G Giles ◽  
P C Poat
Keyword(s):  
Pyruvate Kinase ◽  
Substrate Inhibition ◽  
Carcinus Maenas ◽  
Product Inhibition ◽  
Dead End ◽  
Steady State Kinetic ◽  
Competitive Substrate ◽  
Fructose 1,6 Bisphosphate ◽  
Inhibition Studies ◽  
State Kinetic

1. An investigation of the reaction mechanism of the fructose 1,6-bisphosphate-activated pyruvate kinase isolated from the hepatopancreas of the crab Carcinus maenas was conducted. The enzyme was assayed in the presence of 500 microns-fructose 1,6-bisphosphate, 75 mM-KCl and 8 mM-Mg2+free at 25 degrees C. The results are consistent with a rapid-equilibrium random mechanism. 2. Evidence is presented that suggests the formation of two mixed-substrate-product dead-end complexes, enzyme-ADP-pyruvate and enzyme-ADP-ATP. 3. Competitive substrate inhibition was observed for both substrates, ADP and phosphoenolpyruvate, suggesting the formation of the complexes enzyme-ADP-ADP and enzyme-phosphoenolpyruvate-phosphoenolpyruvate in the suggested mechanism. 4. Data from the ATP product-inhibition studies indicate the formation of the complex enzyme-ATP-ATP. This suggests that in the reverse reaction ATP also will show substrate inhibition. 5. The presence of a saturating concentration of fructose 1,6-bisphosphate does not cause full activation of the purified preparations of the enzyme. 6. Pyruvate kinase activity in the supernatant of a hepatopancreas homogenate was completely activated by fructose 1,6-bisphosphate, suggesting that the binding of this ligand to the purified pyruvate kinase was impaired.

Substrate Inhibition of Pyruvate Kinase Isolated from the Leg Muscle of Carcinus maenas

1976 ◽  
Vol 4 (6) ◽  
pp. 1158-1160 ◽  
Author(s):  
COLIN J. NEWTON ◽  
PETER C. POAT ◽  
KENNETH A. MUNDAY
Keyword(s):  
Pyruvate Kinase ◽  
Substrate Inhibition ◽  
Carcinus Maenas ◽  
Leg Muscle

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.

scholarly journals The kinetic mechanism of the major form of ox kidney aldehyde reductase with d-glucuronic acid

1982 ◽  
Vol 205 (2) ◽  
pp. 381-388 ◽  
Author(s):  
Ann K. Daly ◽  
Timothy J. Mantle
Keyword(s):  
Glucuronic Acid ◽  
Alternative Pathway ◽  
Kinetic Mechanism ◽  
Product Inhibition ◽  
Aldehyde Reductase ◽  
Major Form ◽  
Mechanism Of Inhibition ◽  
Steady State Kinetics ◽  
Inhibition Studies ◽  
Kinetics Of

The steady-state kinetics of the major form of ox kidney aldehyde reductase with d-glucuronic acid have been determined at pH7. Initial rate and product inhibition studies performed in both directions are consistent with a Di-Iso Ordered Bi Bi mechanism. The mechanism of inhibition by sodium valproate and benzoic acid is shown to involve flux through an alternative pathway.

scholarly journals Human glutamic-γ-semialdehyde dehydrogenase. Kinetic mechanism

1989 ◽  
Vol 261 (3) ◽  
pp. 935-943 ◽  
Author(s):  
C Forte-McRobbie ◽  
R Pietruszko
Keyword(s):  
Kinetic Mechanism ◽  
Product Inhibition ◽  
Maximal Velocity ◽  
Semialdehyde Dehydrogenase ◽  
Rate Limiting Step ◽  
Dead End ◽  
Inhibition Studies ◽  
Rate Limiting ◽  
Competitive Pattern ◽  
Pattern Versus

The kinetic mechanism of homogeneous human glutamic-gamma-semialdehyde dehydrogenase (EC 1.5.1.12) with glutamic gamma-semialdehyde as substrate was determined by initial-velocity, product-inhibition and dead-end-inhibition studies to be compulsory ordered with rapid interconversion of the ternary complexes (Theorell-Chance). Product-inhibition studies with NADH gave a competitive pattern versus varied NAD+ concentrations and a non-competitive pattern versus varied glutamic gamma-semialdehyde concentrations, whereas those with glutamate gave a competitive pattern versus varied glutamic gamma-semialdehyde concentrations and a non-competitive pattern versus varied NAD+ concentrations. The order of substrate binding and release was determined by dead-end-inhibition studies with ADP-ribose and L-proline as the inhibitors and shown to be: NAD+ binds to the enzyme first, followed by glutamic gamma-semialdehyde, with glutamic acid being released before NADH. The Kia and Kib values were 15 +/- 7 microM and 12.5 microM respectively, and the Ka and Kb values were 374 +/- 40 microM and 316 +/- 36 microM respectively; the maximal velocity V was 70 +/- 5 mumol of NADH/min per mg of enzyme. Both NADH and glutamate were product inhibitors, with Ki values of 63 microM and 15,200 microM respectively. NADH release from the enzyme may be the rate-limiting step for the overall reaction.

scholarly journals Purification and kinetic properties of ox brain histamine N-methyltransferase

1986 ◽  
Vol 233 (3) ◽  
pp. 669-676 ◽  
Author(s):  
W L Gitomer ◽  
K F Tipton
Keyword(s):  
Acetic Acid ◽  
Steady State ◽  
Mouse Brain ◽  
Initial Rate ◽  
Substrate Inhibition ◽  
Gel Filtration ◽  
Product Inhibition ◽  
Kinetic Properties ◽  
Brain Histamine ◽  
Inhibition Studies

Histamine N-methyltransferase (EC 2.1.1.8) was purified 1100-fold from ox brain. The native enzyme has an Mr of 34800 +/- 2400 as measured by gel filtration on Sephadex G-100. The enzyme is highly specific for histamine. It does not methylate noradrenaline, adrenaline, DL-3,4-dihydroxymandelic acid, 3,4-dihydroxyphenylacetic acid, 3-hydroxytyramine or imidazole-4-acetic acid. Unlike the enzyme from rat and mouse brain, ox brain histamine N-methyltransferase did not exhibit substrate inhibition by histamine. Initial rate and product inhibition studies were consistent with an ordered steady-state mechanism with S-adenosylmethionine being the first substrate to bind to the enzyme and N-methylhistamine being the first product to dissociate.

scholarly journals Comparison of the active sites of the purified carnitine acyltransferases from peroxisomes and mitochondria by using a reaction-intermediate analogue

1993 ◽  
Vol 294 (3) ◽  
pp. 645-651 ◽  
Author(s):  
N Nic a′ Bháird ◽  
G Kumaravel ◽  
R D Gandour ◽  
M J Krueger ◽  
R R Ramsay
Keyword(s):  
Active Sites ◽  
Random Order ◽  
Kinetic Mechanism ◽  
Product Inhibition ◽  
Binding Domains ◽  
Cell Compartments ◽  
Mitochondrial Inner Membrane ◽  
Kinetic Mechanisms ◽  
Carnitine Acyltransferases ◽  
Inhibition Studies

The carnitine acyltransferases contribute to the modulation of the acyl-CoA/CoA ratio in various cell compartments with consequent effects on many aspects of fatty acid metabolism. The properties of the enzymes are different in each location. The kinetic mechanisms and kinetic parameters for the carnitine acyltransferases purified from peroxisomes (COT) and from the mitochondrial inner membrane (CPT-II) were determined. Product-inhibition studies established that COT follows a rapid-equilibrium random-order mechanism, but CPT-II follows a strictly ordered mechanism in which acyl-CoA or CoA must bind before the carnitine substrate. Hemipalmitoylcarnitinium [(+)-HPC], a prototype tetrahedral intermediate analogue of the acyltransferase reaction, inhibits CPT-II 100-fold better than COT. (+)-HPC behaves as an analogue of palmitoyl-L-carnitine with COT. In contrast, with CPT-II(+)-HPC binds more tightly to the enzyme than do substrates or products, suggesting that it is a good model for the transition state and, unlike palmitoyl-L-carnitine, (+)-HPC can bind to the free enzyme. The data support the concept of three binding domains for the acyltransferases, a CoA site, an acyl site and a carnitine site. The CoA site is similar in COT and CPT-II, but there are distinct differences between the carnitine-binding site which may dictate the kinetic mechanism.

scholarly journals Steady-state kinetics of malonyl-CoA synthetase from Bradyrhizobium japonicum and evidence for malonyl-AMP formation in the reaction

1994 ◽  
Vol 297 (2) ◽  
pp. 327-333 ◽  
Author(s):  
Y S Kim ◽  
S W Kang
Keyword(s):  
Steady State ◽  
Bradyrhizobium Japonicum ◽  
Initial Velocity ◽  
Catalytic Mechanism ◽  
Kinetic Mechanism ◽  
Product Inhibition ◽  
Steady State Kinetics ◽  
Malonyl Coa ◽  
Michaelis Constants ◽  
Inhibition Studies

Malonyl-CoA synthetase catalyses the formation of malonyl-CoA directly from malonate and CoA with hydrolysis of ATP into AMP and PP1. The catalytic mechanism of malonyl-CoA synthetase from Bradyrhizobium japonicum was investigated by steady-state kinetics. Initial-velocity studies and the product-inhibition studies with AMP and PPi strongly suggested ordered Bi Uni Uni Bi Ping Pong Ter Ter system as the most probable steady-state kinetic mechanism of malonyl-CoA synthetase. Michaelis constants were 61 microM, 260 microM and 42 microM for ATP, malonate and CoA respectively, and the value for Vmax, was 11.2 microM/min. The t.l.c. analysis of the 32P-labelled products in a reaction mixture containing [gamma-32P]ATP in the absence of CoA showed that PPi was produced after the sequential addition of ATP and malonate. Formation of malonyl-AMP, suggested as an intermediate in the kinetically deduced mechanism, was confirmed by the analysis of 31P-n.m.r. spectra of an AMP product isolated from the 18O-transfer experiment using [18O]malonate. The 31P-n.m.r. signal of the AMP product appeared at 0.024 p.p.m. apart from that of [16O4]AMP, indicating that one atom of 18O transferred from [18O]malonate to AMP through the formation of malonyl-AMP. Formation of malonyl-AMP was also confirmed through the t.l.c. analysis of reaction mixture containing [alpha-32P]ATP. These results strongly support the ordered Bi Uni Uni Bi Pin Pong Ter Ter mechanism deduced from initial-velocity and product-inhibition studies.

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