scholarly journals Kinetics of the inhibition of human leucocyte elastase by eglin from the leech Hirudo medicinalis

1984 ◽  
Vol 218 (3) ◽  
pp. 829-833 ◽  
Author(s):  
A Baici ◽  
U Seemüller
Keyword(s):  
Steady State ◽  
Complex Formation ◽  
Rate Constants ◽  
Biological Significance ◽  
Hirudo Medicinalis ◽  
Inhibition Mechanism ◽  
Steady State Kinetic ◽  
Leucocyte Elastase ◽  
Kinetics Of ◽  
State Kinetic

The rate constants for the inhibition of human leucocyte elastase by eglin from the leech Hirudo medicinalis were determined by using a pre-steady-state kinetic approach. kon and koff for complex-formation and dissociation were 1 × 10(6)M-1 X S-1 and 8 × 10(-4)S-1 respectively. Ki was calculated as the ratio koff/kon = 8 × 10(-10)M, the binding of eglin to elastase was reversible and the inhibition mechanism was of the fully competitive type. The mechanistic properties of the system and the biological significance of the rate constants are discussed.

Nonlinear steady-state kinetics of chloramphenicol acetyltransferase

1991 ◽  
Vol 69 (9) ◽  
pp. 630-634
Author(s):  
M. James C. Crabbe ◽  
Derek Goode
Keyword(s):  
Steady State ◽  
Chloramphenicol Acetyltransferase ◽  
Binding Region ◽  
Medium Effects ◽  
Acetyl Coa ◽  
Acetyl Coenzyme A ◽  
Steady State Kinetics ◽  
Steady State Kinetic ◽  
Kinetics Of ◽  
State Kinetic

Steady-state kinetic analysis of chloramphenicol acetyltransferase showed that medium effects (higher temperatures or pH, higher ionic strengths, or lower values for dielectric constant) altered the kinetic behaviour of the enzyme with acetyl-CoA as substrate, but did not significantly affect behaviour with chloramphenicol. This was manifest as an increase in the degree of the rate equation to a 2:2 function. This is interpreted in terms of perturbations to the enzyme at or near the acetyl-CoA binding region of the enzyme.Key words: acetyl coenzyme A, chloramphenicol, antibiotics, enzyme kinetics.

scholarly journals Interpretation of the Kinetics of Consecutive Enzyme-catalysed Reactions: Studies on the Arginase-Ornithine Carbamoyltransferase System

1982 ◽  
Vol 35 (2) ◽  
pp. 137 ◽  
Author(s):  
RD Teasdale ◽  
PD Jeffrey ◽  
PW Kuchel ◽  
LW Nichol
Keyword(s):  
Steady State ◽  
Ornithine Carbamoyltransferase ◽  
Enzyme Substrate ◽  
Steady State Kinetic ◽  
Kinetic Mechanisms ◽  
Heterogeneous Association ◽  
Kinetics Of ◽  
State Kinetic ◽  
Enzymic Assay

A method that permits the use of measurements on the concentration of the intermediate in a coupled enzymic assay in determining the presence or absence of an interaction between the enzymes is presented. The method is shown to be closely analogous to a previously formulated procedure involving the determination of the rate of production of the final product of such a sequence and is shown to be applicable regardless of the complexity of the operative kinetic mechanisms, provided it may be assumed that all enzyme-substrate complexes are in the steady-state. Kinetic results obtained with the arginase--ornithine carbamoyltransferase couple, in which the intermediate ornithine is monitored, are examined in these terms to conclude that no heterogeneous association is operative between the enzymes.

The Steady State Kinetics of Plasmin and Trypsin Catalysed Hydrolysis of a Number of Tripeptideanilides

1979 ◽  
Author(s):  
U. Christensen ◽  
H-H. Ipsen
Keyword(s):  
Steady State ◽  
Kinetic Parameters ◽  
Amino Group ◽  
Steady State Kinetics ◽  
Steady State Kinetic ◽  
Ph Range ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
State Kinetic

The steady state kinetic parameters of plasmin and trypsin catalysed hydrolysis of Bz-L-Phe-Val-Arg-pNA, L-Phe-Val-Arg-pNA, Bz-D-Phe-Val-Arg-pNA, D-Phe-Val-Arg-pNA and D-Val-Leu-Lys-pNA in the pH-range 6-9 are presented. Ionization of catalytically essential enzymic groups accounts satisfactorily for the pH-dependencies of the kinetic parameters for plas-rain and trypsin reactions with Bz-L-Phe-Val-Arg-pNA, Bz-D-Phe-Val-Arg-pNA and D-Val-Leu-Lys-pNA. The protonation of the α-amino group of L-Phe-Val-Arg-pNA and D-Phe-Val-Arg-pNA (pK=7.0) show some additional effect. The values of the catalytic constants for plasmin and trypsin reactions with these p-nitroanilides are alike those normally found for specific ester substrates, indicating that the deacylation steps are rate determining.

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