The Effects of Substrate Concentration on the Mg-Adenosine Triphosphatase Activity of Myosin

1975 ◽  
Vol 53 (12) ◽  
pp. 1282-1287 ◽  
Author(s):  
T. Nihei ◽  
C. A. Filipenko
Keyword(s):  
Steady State ◽  
Substrate Concentration ◽  
Active Sites ◽  
Adenosine Triphosphatase ◽  
Kinetic Studies ◽  
Heavy Meromyosin ◽  
Adenosine Triphosphatase Activity ◽  
Steady State Rate ◽  
State Rate ◽  
Substrate Concentrations

Using myosin, heavy meromyosin, and subfragment-1 the steady state rate of Mg-modified adenosine triphosphatase (Mg-ATPase) was determined over a range of substrate concentrations between 10−8 M and 5 × 10−3 M, at 0.5 M and 0.05 M KCl (pH 7.4 at 20 °C). At the substrate concentrations below 10−5 M, myosin Mg-ATPase was observed to show that two active sites interact, as suggested by the analysis of transient kinetic studies (Walz, F. G., Jr.: J. Theor. Biol. 41, 357–373 (1973)). The increase in the activity at Mg-ATP concentrations higher than 10−4 M corresponds to the binding of Mg-ATP to myosin sites not responsible for the catalytic action. With heavy meromyosin and subfragment-1, the activity was best expressed by the Michaelis equation. With heavy meromyosin, the activation at high ATP concentrations is detectable, though not as pronounced as with myosin, but not with subfragment-1.

THEORY OF THE TRANSIENT PHASE IN KINETICS, WITH SPECIAL REFERENCE TO ENZYME SYSTEMS: II. THE CASE OF TWO ENZYME–SUBSTRATE COMPLEXES

1956 ◽  
Vol 34 (2) ◽  
pp. 146-150 ◽  
Author(s):  
Ludovic Ouellet ◽  
Keith J. Laidler
Keyword(s):  
Steady State ◽  
Substrate Concentration ◽  
Kinetic Scheme ◽  
Rate Equations ◽  
Theoretical Treatment ◽  
Transient Phase ◽  
Enzyme Substrate ◽  
Enzyme Systems ◽  
Steady State Rate ◽  
State Rate

A theoretical treatment is worked out for the kinetic scheme[Formula: see text]in which two enzyme–substrate complexes are formed consecutively. The steady-state rate equations are obtained, and equations are given for the transient phase subject to the condition that the substrate concentration is greatly in excess of that of the enzyme. Some kinetic consequences of the resulting equations are discussed.

scholarly journals Kinetic studies on the esterase activity of cytoplasmic sheep liver aldehyde dehydrogenase

1978 ◽  
Vol 171 (3) ◽  
pp. 533-538 ◽  
Author(s):  
A K H MacGibbon ◽  
S J Haylock ◽  
P D Buckley ◽  
L F Blackwell
Keyword(s):  
Steady State ◽  
Aldehyde Dehydrogenase ◽  
Kinetic Studies ◽  
Sheep Liver ◽  
Rate Limiting Step ◽  
Dehydrogenase Reaction ◽  
Steady State Rate ◽  
Michaelis Constants ◽  
State Rate ◽  
Liver Aldehyde Dehydrogenase

The hydrolysis of 4-nitrophenyl acetate catalysed by cytoplasmic aldehyde dehydrogenase (EC 1.2.1.3) from sheep liver was studied by steady-state and transient kinetic techniques. NAD+ and NADH stimulated the steady-state rate of ester hydrolysis at concentrations expected on the basis of their Michaelis constants from the dehydrogenase reaction. At higher concentrations of the coenzymes, both NAD+ and NADH inhibited the reaction competitively with respect to 4-nitrophenyl acetate, with inhibition constants of 104 and 197 micron respectively. Propionaldehyde and chloral hydrate are competitive inhibitors of the esterase reaction. A burst in the production of 4-nitrophenoxide ion was observed, with a rate constant of 12 +/- 2s-1 and a burst amplitude that was 30% of that expected on the basis of the known NADH-binding site concentration. The rate-limiting step for the esterase reaction occurs after the formation of 4-nitrophenoxide ion. Arguments are presented for the existence of distinct ester- and aldehyde-binding sites.

A COMPARISON BETWEEN THE INITIAL RATE EXPRESSIONS OBTAINED UNDER STRICT CONDITIONS AND THE RAPID EQUILIBRIUM ASSUMPTION USING, AS EXAMPLE, A FOUR SUBSTRATE ENZYME REACTION

2011 ◽  
Vol 10 (05) ◽  
pp. 659-678
Author(s):  
J. M. YAGO ◽  
C. GARRIDO-DEL SOLO ◽  
M. GARCIA-MORENO ◽  
R. VARON ◽  
F. GARCIA-SEVILLA ◽  
...  
Keyword(s):  
Steady State ◽  
Rate Equation ◽  
Initial Rate ◽  
Enzyme Reaction ◽  
Rate Equations ◽  
Steady State Rate ◽  
State Rate ◽  
Rapid Equilibrium ◽  
Kinetics Of ◽  
Substrate Concentrations

The software WinStes, developed by our group, is used to derive the strict steady-state initial rate equation of the reaction mechanism of CTP:sn-glycerol-3-phosphate cytidylyltransferase [EC 2.7.7.39] from Bacillus subtilis. This enzyme catalyzes a reaction with two substrates and operates by a random ordered binding mechanism with two molecules of each substrate. The accuracy of the steady-state rate equation derived is checked by comparing the rate values it provides with those obtained from the simulated progress curves. To analyze the kinetics of this enzyme using the strict steady-state initial rate equation, several curves for different substrate concentrations and different rate constants are generated. A comparison of these curves with the curves obtained from the rapid equilibrium initial rate equation, with different substrate concentration values, serves to analyze how the strict steady-state rate equation values are closer to those of rapid equilibrium rate equations when rapid equilibrium conditions are fulfilled.

scholarly journals Fate of the SpoIIAB*-ADP Liberated after SpoIIAB Phosphorylates SpoIIAA of Bacillus subtilis

2000 ◽  
Vol 182 (21) ◽  
pp. 6250-6253 ◽  
Author(s):  
Chung-Sheng Lee ◽  
Isabelle Lucet ◽  
Michael D. Yudkin
Keyword(s):  
Bacillus Subtilis ◽  
Steady State ◽  
Protein Kinase ◽  
Ternary Complex ◽  
Enzymatic Reaction ◽  
Kinetic Studies ◽  
Active State ◽  
Steady State Rate ◽  
Catalytically Active ◽  
State Rate

ABSTRACT Phosphorylation of SpoIIAA catalyzed by SpoIIAB helps to regulate the first sporulation-specific ς factor, ςF, ofBacillus subtilis. The steady-state rate of phosphorylation is known to be exceptionally slow and to be limited by the return of the protein kinase, SpoIIAB, to a catalytically active state. Previous work from this laboratory has suggested that, after catalyzing the phosphorylation, SpoIIAB is in a form (SpoIIAB*) that does not readily release ADP. We now show that the rate of release of ADP from the SpoIIAB*-ADP complex was much diminished by the presence of unreacted SpoIIAA, suggesting that SpoIIAA can form a long-lived ternary complex with SpoIIAB*-ADP in which the SpoIIAB* form is stabilized. In kinetic studies of the phosphorylation of SpoIIAA, the ternary complex SpoIIAA-SpoIIAB*-ADP could be distinguished from the short-lived complex SpoIIAA-SpoIIAB-ADP, which can be readily produced in the absence of an enzymatic reaction.

Corticosterone secretion in rats as a function of ACTH input and adrenal blood flow

1965 ◽  
Vol 209 (4) ◽  
pp. 811-814 ◽  
Author(s):  
John C. Porter ◽  
M. S. Klaiber
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Steady Increase ◽  
Constant Input ◽  
Corticosterone Secretion ◽  
Steady State Rate ◽  
State Rate

The rate of secretion of corticosterone from the left adrenal of rats receiving a constant input of ACTH was determined for different flows of blood through the adrenal during the 2- to 3-hr interval following hypophysectomy. Two hours after hypophysectomy the secretion of corticosterone was low in all groups regardless of flow. An input of 0.26 mU ACTH/min caused a steady increase in secretion for 30–40 min before a steady-state rate was attained. The average steady-state rate of secretion was 1.1, 2.4, 3.5, 6.2, 7.2, 6.2, and 6.2 µg/5 min for flows of 0.005, 0.012, 0.023, 0.034, 0.039, 0.051, and 0.058 ml/min, respectively. Under the conditions of these experiments where the input of ACTH was 0.26 mU/min the secretion of corticosterone increased significantly with time of input of ACTH and with flow of blood through the adrenal.

scholarly journals The Natural Rate of Interest and the Optimal Rate of Interest in the Steady State

2021 ◽  
pp. 17-41
Author(s):  
Carl Christian von Weizsäcker ◽  
Hagen M. Krämer
Keyword(s):  
Steady State ◽  
Public Debt ◽  
Fundamental Equation ◽  
Optimal Rate ◽  
Natural Rate ◽  
Real Rate ◽  
Capital Theory ◽  
Steady State Rate ◽  
Natural Rate Of Interest ◽  
State Rate

AbstractThe “natural rate of interest” is the hypothetical, risk-free real rate of interest that would obtain in a closed economy, if net public debt were zero. It is considerably less than the optimal steady-state rate of interest, which is equal to the system’s growth rate. This holds for a very general “meta-model.” The fundamental equation of capital theory holds on the optimal steady-state path: T = Z − D, where T is the overall economic period of production, Z is the representative private “waiting period” of consumers and D is the public debt ratio. Prosperity is at least 30% lower at the natural rate of interest than at the optimal rate.

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