A Kinetic Analysis of Rabbit Muscle Pyruvate Kinase in the Reverse Direction

1975 ◽  
Vol 3 (2) ◽  
pp. 312-314 ◽  
Author(s):  
IAN G. GILES ◽  
PETER C. POAT ◽  
KENNETH A. MUNDAY
Keyword(s):  
Kinetic Analysis ◽  
Pyruvate Kinase ◽  
Reverse Direction ◽  
Rabbit Muscle ◽  
Muscle Pyruvate Kinase

scholarly journals The kinetics of rabbit muscle pyruvate kinase. Initial-velocity, substrate- and product-inhibition and isotopic-exchange studies of the reverse reaction

1976 ◽  
Vol 157 (3) ◽  
pp. 577-589 ◽  
Author(s):  
I G Giles ◽  
P C Poat ◽  
K A Munday
Keyword(s):  
Pyruvate Kinase ◽  
Isotopic Exchange ◽  
Initial Rate ◽  
Substrate Inhibition ◽  
Product Inhibition ◽  
Reverse Direction ◽  
Rabbit Muscle ◽  
Muscle Enzyme ◽  
Rapid Equilibrium ◽  
Muscle Pyruvate Kinase

1. An assay, based on the transfer of label from [gamma-32P]ATP to [32P]phosphoenolpyruvate, suitable for a steady-state kinetic analysis of pyruvate kinase in the reverse direction (i.e. phosphoenolpyruvate synthesis), is described. 2. This assay was used in a kinetic investigation of the rabbit muscle enzyme including initial-rate and product-inhibition experiments, at a pH of 7.4 and constant concentrations of total K+ and free Mg2+. 3. These studies indicate that there is a random release of ADP and phosphoenolpyruvate from the enzyme and that there is a competitive substrate inhibition by ATP. Some of the results were suggestive that the rapid-equilibrium assumption, generally used for this enzyme was not valid. 4. Techniques were developed to measure the rate of isotopic exchange between all the substrate-product pairs. 5. By using these techniques the rates of isotopic exchange at chemical equilibrium were measured. The results indicate that this enzyme does not catalyse a truly rapid-equilibrium random mechanism, although in the forward reaction all initial-rate data obtained to date are consistent with this assumption.

Interaction of D-phenylalanine with Co(II)-substituted rabbit muscle pyruvate kinase: kinetic and optical properties

1982 ◽  
Vol 60 (9) ◽  
pp. 861-866
Author(s):  
Chiu-Yin Kwan ◽  
Robert C. Davis
Keyword(s):  
Amino Acids ◽  
Optical Properties ◽  
Pyruvate Kinase ◽  
Conformational Changes ◽  
Metal Ion ◽  
Inhibitory Effect ◽  
Rabbit Muscle ◽  
Divalent Metal Ion ◽  
Muscle Pyruvate Kinase ◽  
Difference Absorption

The kinetic and optical properties of Co(II)-substituted pyruvate kinase in the presence of D-phenylalanine (D-Phe) were investigated. The results are discussed in comparison with the effects of its optical isomer L-phenylalanine (L-Phe) on the same enzyme. The catalytic effect of D-Phe on rabbit muscle pyruvate kinase depended upon the nature of the activating divalent metal ion used. It has stimulatory effect on Mg(II)-activated enzyme, but inhibitory effect on Co(II)-activated enzyme. Unlike the inhibitory effect of L-Phe, the inhibition of Co(II)–enzyme by D-Phe was not sensitive to the changes of pH and temperature, could not be reversed by L-alanine (L-Ala), displayed hyperbolic kinetics, and was noncompetitive with respect to phosphoenolpyruvate saturation. D-Phe induced substantial visible circular dichroism (CD) spectral changes of Co(II)–enzyme similar to those induced by L-Phe. Although ultraviolet CD spectrum was not affected, D-Phe induced an ultraviolet difference absorption spectral change very similar to, but much smaller than, that induced by L-Phe. Our results support that D-Phe and other amino acids interact with the enzyme at two different sites: a common site, causing similar conformational changes which bear little direct kinetic relevance, and a kinetically relevant site, which is sterically dependent upon the side chain of the amino acids.

scholarly journals A kinetic study of rabbit muscle pyruvate kinase

1973 ◽  
Vol 131 (2) ◽  
pp. 223-236 ◽  
Author(s):  
S. Ainsworth ◽  
N. Macfarlane
Keyword(s):  
Reaction Mechanism ◽  
Kinetic Study ◽  
Pyruvate Kinase ◽  
Random Order ◽  
Experimental Results ◽  
Rabbit Muscle ◽  
Dead End ◽  
Inhibition Constants ◽  
Muscle Pyruvate Kinase ◽  
Kinetics Of

The paper reports a study of the kinetics of the reaction between phosphoenolpyruvate, ADP and Mg2+ catalysed by rabbit muscle pyruvate kinase. The experimental results indicate that the reaction mechanism is equilibrium random-order in type, that the substrates and products are phosphoenolpyruvate, ADP, Mg2+, pyruvate and MgATP, and that dead-end complexes, between pyruvate, ADP and Mg2+, form randomly and exist in equilibrium with themselves and other substrate complexes. Values were determined for the Michaelis, dissociation and inhibition constants of the reaction and are compared with values ascertained by previous workers.

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