Kinetic manifestations of allosteric interactions in models of regulatory enzymes with “indirect” co-operativity

Bi, Kurganov; Kagan, Z. S.; Dorozhko, A.I.; Yakovlev, V.A.

doi:10.1016/0022-5193(74)90096-4

Cited by 17 publications

(2 citation statements)

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“…acteristic of an associating-dissociating system in which only an associated form of the enzyme is active (Frieden, 1981; Kurganov, 1973Kurganov, , 1974Kurganov et al, 1974). Such selfassociating systems can give rise to nonhyperbolic kinetics such as the positive cooperativity observed when the activity of CTP synthetase is measured as a function of either ATP or UTP concentration while the concentration of the other is nonsaturating.…”

Section: Resultsmentioning

confidence: 99%

“…The effects of enzyme concentration on the kinetic properties of CTP synthetase and the hysteretic properties of CTP synthetase described in this paper represent previously unreported properties of this enzyme which also need to be taken into consideration as a basis for explaining the cooperativity exhibited by the enzyme for ATP and UTP, as well as, perhaps, other properties of CTP synthetase such as the negative cooperativity exhibited for the substrate glutamine and for GTP, an allosteric effector. It has been well established that the properties of association-dissociation and of hysteresis in an enzyme can give rise to cooperativity and may play a significant role in the regulatory properties of an enzyme (Neet, 1980a,b;Frieden, 1981;Nichol et al, 1967;Nichol & Winzor, 1976;Kurganov, 1973Kurganov, , 1974Kurganov, , 1977Kurganov et al, 1974).…”

Section: Discussionmentioning

confidence: 99%

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CTP synthetase from Escherichia coli: an improved purification procedure and characterization of hysteretic and enzyme concentration effects on kinetic properties

Anderson¹

1983

Biochemistry

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Previous studies have shown that CTP synthetase exists as a dimer which aggregates to a tetramer in the presence of the substrates ATP and UTP [Long, C. W., Levitzki, A., & Koshland, D. E., Jr. (1970) J. Biol. Chem. 245, 80]. A new, relatively simple purification procedure resulting in enzyme of high purity and in good yield has been established by using two successive hydrophobic chromatography steps, the first in the absence of ATP and UTP (dimer binds) and the second in the presence of ATP and UTP (tetramer does not bind). Several previously unreported properties of CTP synthetase are described which suggest that alterations in the state of association and dissociation of the enzyme have a controlling influence on the observed kinetic properties of the enzyme. The specific activity of CTP synthetase decreases with decreasing enzyme concentration, particularly when the concentrations of ATP and UTP in the reaction mixture are nonsaturating. The concentration of ATP or UTP required for half-maximal activity is significantly increased as the concentration of enzyme in the reaction mixture is decreased. CTP synthetase displays reversible cold lability and hysteretic properties (lags or bursts in the time course of product formation), both of which are influenced by the concentration of enzyme and/or the presence of ATP and UTP in the preincubation mixture and/or assay mixture. Gel filtration studies have shown that CTP synthetase can dissociate to an apparently inactive monomer. The dissociation is reversible, and the rate of association is slow.

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Section: Resultsmentioning

confidence: 99%