scholarly journals Kinetics of protein modification, and/or enzyme inactivation, reactions by an unstable modifying agent

1987 ◽  
Vol 246 (3) ◽  
pp. 803-806 ◽  
Author(s):  
E T Rakitzis
Keyword(s):  
Protein Modification ◽  
Enzyme Inactivation ◽  
Modifying Agent ◽  
Kinetics Of

scholarly journals Kinetics of protein-modification reactions. Stoichiometry of modification-produced enzyme inactivation: modification of rhodanese by 2,4,6-trinitrobenzenesulphonic acid

1985 ◽  
Vol 230 (1) ◽  
pp. 89-93 ◽  
Author(s):  
E T Rakitzis ◽  
T B Malliopoulou
Keyword(s):  
Protein Modification ◽  
Reaction Medium ◽  
Enzyme Inactivation ◽  
Mathematical Treatment ◽  
Modifying Agent ◽  
Catalytic Function ◽  
Reactive Groups ◽  
Decreasing Ph ◽  
Activity Loss ◽  
Kinetics Of

A mathematical treatment is presented for the dependence of enzyme activity loss on the numbers and reactivities of the groups essential for catalytic function, when enzyme protein modification is carried out by the use of concentrations of protein reactive groups well in excess of that of modifying agent. Experimentally obtained data on the modification of rhodanese (thiosulphate sulphurtransferase, EC 2.8.1.1) by 2,4,6-trinitrobenzenesulphonic acid are presented, and it is shown that, at pH9.00, the fractional concentration of rhodanese groups, or of rhodanese group reactivities, essential for enzyme catalytic function is 0.88; this value is found to decrease with decreasing pH of the reaction medium. The possibility that rhodanese inactivation by 2,4,6-trinitrobenzenesulphonic acid is brought about by modification of groups other than amino groups is ruled out by a comparison of the enzyme-inactivation and protein-modification stoichiometries, for putative reaction models for enzyme and modifying agent.

Thermal kinetics of enzyme inactivation, color changes, and allicin degradation of garlic under blanching treatments

2019 ◽  
Vol 42 (3) ◽  
pp. e12991 ◽  
Author(s):  
Zhi Huang ◽  
Quan Zhou ◽  
Wei‐Liang Wu ◽  
Jun Wan ◽  
Ai‐Min Jiang
Keyword(s):  
Enzyme Inactivation ◽  
Color Changes ◽  
Thermal Kinetics ◽  
Kinetics Of

Drying characteristic, enzyme inactivation and browning pigmentation kinetics of controlled humidity-convective drying of banana slices

2018 ◽  
Vol 54 (10) ◽  
pp. 3117-3130 ◽  
Author(s):  
Frederick Sarpong ◽  
Xiaojie Yu ◽  
Cunshan Zhou ◽  
Patricia Oteng-Darko ◽  
Leticia Peace Amenorfe ◽  
...  
Keyword(s):  
Enzyme Inactivation ◽  
Convective Drying ◽  
Kinetics Of

scholarly journals Inactivation of penicillin acylase from Kluyvera citrophila by N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline: a case of time-dependent non-covalent enzyme inhibition

1993 ◽  
Vol 291 (3) ◽  
pp. 907-914 ◽  
Author(s):  
J Martín ◽  
J M Mancheño ◽  
R Arche
Keyword(s):  
Enzyme Assay ◽  
Ph Dependence ◽  
Penicillin Acylase ◽  
Enzyme Inactivation ◽  
Time Dependent ◽  
Penicillin G ◽  
Reversible Binding ◽  
Ph Increase ◽  
Kinetics Of ◽  
Covalent Activation

Penicillin acylase (PA) from Kluyvera citrophila was inhibited by N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ), a specific carboxy-group-reactive reagent. Enzyme activity progressively decreased to a residual value depending on EEDQ concentration. Neither enzymic nor non-enzymic decomposition of EEDQ is concomitant with PA inactivation. Moreover, enzyme re-activation is achieved by chromatographic removal of EEDQ, pH increase or displacement of the reagent with penicillin G. It was then concluded that PA inactivation is due to an equilibrium reaction. The kinetics of enzyme inactivation was analysed by fitting data to theoretical equations derived in accordance with this mechanism. Corrections for re-activation during the enzyme assay were a necessary introduction. The pH-dependence of the rate constant for EEDQ hydrolysis either alone or in the presence of enzyme was studied by u.v. spectroscopy. It turned out to be coincident with the pH-dependence of the forward and reverse rate constants for the inactivation process. It is suggested that previous protonation of the EEDQ molecule is required for these reactions to occur. The thermodynamic values associated with the overall reaction showed little change. Finally it is proposed that the inactivation of PA by EEDQ proceeds through a two-step reaction. The initial and rapid reversible binding is followed by a slow, time-dependent, non-covalent, reversible inactivating step. The expected behaviour in the case of enzyme modification by covalent activation of carboxy residues is also reviewed.

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