Kinetics of irreversible enzyme inhibition: Co-operative effects

Rakitzis, Emmanuel T.

doi:10.1016/0022-5193(77)90184-9

Cited by 29 publications

(15 citation statements)

References 27 publications

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“…The inhibitor-resistant portion of the flux may represent (i) leakage in the red cell membrane (which would include the reversibly inhibited portion), (ii) a subsidiary sulfate carrier system that is totally resistant to inactivation by the inhibitors used, (iii) attachment of the irreversible inhibitor on the active site of the protein functioning unit, but in such a manner that only part of the activity of the unit is destroyed (Ray & Koshland, 1961), or (iv) negative irreversible inhibitor cooperativity, e.g., the covalent attachment of one or more irreversible inhibitor molecules to the protein transport unit, but at a site other than the active site of the unit, so that the modified protein unit is resistant to inhibitor attachment (Levy, Leber & Ryan, 1963;Kitchen & Andrews, 1974;Magee & Ebner, 1974;Schram & Lawson, 1963;Rakitzis, 1977). Kinetic evidence alone is insufficient to distinguish between all the above possibilities.…”

Section: K(t)=k R (A+ E Bi E-k~mentioning

confidence: 98%

“…The solution requires that A+ ~ B~= 1, where m is an empirically i=1 derived parameter giving the number of exponential terms in the rate expression. The theory has been derived in detail in a previous paper (Rakitzis, 1977).…”

Section: K(t)=k R (A+ E Bi E-k~mentioning

confidence: 99%

“…will become a time-dependent function with the onset of irreversible modification of the anion transport system, i.e., k,(t) where the ratio kr(t)/k r would equal the fraction of the transport sites not irreversibly bound by inhibitor. If the inhibitor binding sites, at which irreversible modification occurs, are uniform and independent (Ray & Koshland, 1961;Rakitzis, 1977) k~ (t) = e-kt (2) k~ where k is the inactivation constant. In the most general case, where the inhibitor binding sites may be nonuniform or interacting,…”

Section: Kinetic Analysis Of Anion Transport In Human Red Cells In Thmentioning

confidence: 99%

“…Therefore, k~A, k,B and k can be determined by graphical methods (Defares & Sneddon, 1960). By definition A +B= 1 (Rakitzis, 1977); therefore, k,=k,A +k~B, and kr, A and B can be computed.…”

Section: K(t)=k R (A+ E Bi E-k~mentioning

confidence: 99%

“…A kinetic analysis of the inhibition of sulfate transport in human red cells by three water-soluble isothiocyanates is reported here. An attempt is made to answer two questions concerning the inhibition of anion transport: (i) whether the reversible binding of isothiocyanate on the cell membrane has an effect on anion transport, and (ii)whether the sites on the cell membrane to which isothiocyanate binds irreversibly are uniform and independent, i.e., whether the time dependence of transport inactivation can be described by a single exponential rather than by a summation of exponentials (Ray & Koshland, 1961Rakitzis, 1977).…”

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Kinetic analysis of the inhibition of sulfate transport in human red blood cells by isothiocyanates

1978

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A kinetic analysis of anion self-exchange in human red blood cells, in the presence of an irreversible inhibitor, is presented and applied to the study of the inactivation of sulfate transport by three isothiocyanates: 3-isothiocyano-1,5-naphthalenedisulfonic acid, disodium salt (INDS), 1-isothiocyano-4-naphthalene sulfonic acid, sodium salt, monohydrate (INS), and 1-isothiocyano-4-benzenesulfonic acid, sodium salt, monohydrate (IBS). The time dependence of the inhibition of sulfate transport by the isothiocyanates used could be described by a single exponential and could be shown to contain a reversible and an irreversible component. In each case a portion of sulfate efflux was found to be resistant to inactivation. The residual portion of the sulfate efflux varied with inhibitor: 4% for INS, 16% for INDS, and 34% for IBS. INS showed the largest reversible inhibitory effect (12% of the flux remaining at 0.2 mM inhibitor concentration), while INDS showed the weakest effect (92% of the flux remaining at 0.3 mM inhibitor concentration). IBS had the highest rate of inactivation while INDS had the lowest. The kinetic analysis further suggests that all three isothiocyanates bind reversibly to an inhibitory site on the membrane before they bind covalently, and therefore irreversibly, to the same site on the membrane. The equilibrium constant for the dissociation of the reversibly-bound complex, Ki, and the rate of irreversible inactivation after all membrane sites are reversibly bound, kmax, have been computed for all three inhibitors: INDS (Ki = 420 micron, kmax = 5.04 hr-1), INS (Ki = 148 micron, kmax = 6.48 hr-1), and IBS (Ki = 208 micron, k(max) = 8.11 hr-1).

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Section: K(t)=k R (A+ E Bi E-k~mentioning

confidence: 98%

Section: K(t)=k R (A+ E Bi E-k~mentioning

confidence: 99%

Section: Kinetic Analysis Of Anion Transport In Human Red Cells In Thmentioning

confidence: 99%

Section: K(t)=k R (A+ E Bi E-k~mentioning

confidence: 99%

mentioning

confidence: 99%

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Kinetic analysis of the inhibition of sulfate transport in human red blood cells by isothiocyanates

1978

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Kinetic analysis of biphasic protein modification reactions

Rakitzis

1980

J. Math. Biology

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A mathematical analysis of biphasic protein modification reactions is presented, and it is shown that, in addition to the protein species modification reactions, one more time-dependent step must be postulated to exist in the reaction process. This step involves the interconversion of the different protein species, such as binding of ligand with protein, or the change in the isomerization state of the protein. The kinetic description of the reaction process is effected through a second order homogeneous linear differential equation, with time as the independent variable, and unmodified protein concentration as the dependent variable. A simple procedure of graphical analysis of the experimental data is described, and it is shown that, by a process of elimination, the nature of the protein species interconversion time-dependent step may be recognized, and also the dependence of the protein species inactivation rate constants on various parameters in the preparation may be evaluated. The method is illustrated by the detailed analysis of one example from the literature, the inactivation of phosphorylase b by 5,5-dithiobis (2-nitrobenzoic acid).

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Chemical modification of enzymes: Critical evaluation of the graphical correlation between residual enzyme activity and number of groups modified

Stevens

Colman

1980

Bltn Mathcal Biology

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Kinetics of irreversible enzyme inhibition: Co-operative effects

Cited by 29 publications

References 27 publications

Kinetic analysis of the inhibition of sulfate transport in human red blood cells by isothiocyanates

Kinetic analysis of the inhibition of sulfate transport in human red blood cells by isothiocyanates

Kinetic analysis of biphasic protein modification reactions

Chemical modification of enzymes: Critical evaluation of the graphical correlation between residual enzyme activity and number of groups modified

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