The activation of <scp>l</scp>-threonine dehydrogenase by potassium ions

Green, Margaret L.

doi:10.1042/bj0920550

Cited by 13 publications

(9 citation statements)

References 15 publications

(3 reference statements)

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“…It has been previously suggested that the inhibition of monoamine oxidase by hydrazine derivatives may involve a catalytic effect of the enzyme (Davison, 1957;Zeller & Sarkar, 1962;Bloom, 1963;Smith et al, 1963;Green, 1964;McEwen et al, 1969). The mechanism proposed here is similar to that proposed by Davison (1957) and is in accord with the observations that the efficiency of hydrazine inhibition parallels the efficiency with which the parent amines are oxidized by monoamine oxidase (Zeller et al, 1960;Bloom, 1963).…”

Section: Discussionsupporting

confidence: 78%

“…Davison (1957) demonstrated an oxygen requirement for the inhibition of monoamine oxidase by iproniazid (1-isonicotinoyl-2-isopropylhydrazine); however, Smith et al (1963) suggested that the presence of oxygen may be required for the non-enzymic conversion ofiproniazid into isopropylhydrazine, which might be the actual inhibiting species. However, the presence of oxygen has been shown to be necessary for the inhibition of monoamine oxidase by hydrazine derivatives by Green (1964) and Tipton (1971a). Clineschmidt & Horita (1969a,b) showed that the inhibitor phenethylhydrazine was a substrate as well as an inhibitor for monoamine oxidase in rat liver mitochondria, and Tipton & Spires (1972) showed that the immediate product of this oxidation was the corresponding hydrazone, phenethylidenehydrazine.…”

mentioning

confidence: 99%

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Inhibition of monoamine oxidase by substituted hydrazines

Tipton¹

1972

Biochemical Journal

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1. The initial rate of inhibition of monoamine oxidase by phenethylhydrazine was shown to be similar, in pH-dependence and kinetic properties, to the oxidation of that compound by monoamine oxidase. 2. The time-course of irreversible inhibition of monoamine oxidase by phenethylhydrazine lags behind that of reversible inhibition. 3. Hydralzine was shown to be a reversible competitive inhibitor of monoamine oxidase, but phenylhydrazine is an irreversible inhibitor. Inhibition by the latter compound is not affected by the absence of oxygen, and the presence of substrate exerts no protective action. 4. Hydrazine does not inhibit monoamine oxidase unless a substrate and oxygen are present. 5. Phenethylidenehydrazine was found to be a time-dependent inhibitor of monoamine oxidase and the rate of inhibition was hindered by increasing oxygen concentration. 6. A mechanism for the inhibition of the enzyme by phenethylhydrazine is proposed in which the product of oxidation of this compound is a potent reversible inhibitor and an irreversible inhibitor of the enzyme. A computer simulation of such a mechanism predicts time-courses of inhibition that are in reasonable agreement with those observed experimentally.

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Section: Discussionsupporting

confidence: 78%

mentioning

confidence: 99%

Inhibition of monoamine oxidase by substituted hydrazines

Tipton¹

1972

Biochemical Journal

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“…247, 248 Green has suggested that copper-catalyzed decomposition of hydrazine derivatives might occur in the vicinity of the enzyme's active center generating radical species which would inhibit MA0 irreversibly. 249 The mechanism of MA0 inhibition by phenylhydrazine has been particularly studied. The initial reaction is reduction of the flavine by phenylhydrazine to form phenyldiazene which decomposes to form a covalent C(4a)-phenyl dihydroflavin adduct or to react with protein groups involved in acti~ity.…”

Section: B Hydrazine Derivativesmentioning

confidence: 99%

Interactions of monoamine oxidase with substrates and inhibitors

Dostert

Benedetti

Tipton

1989

Medicinal Research Reviews

143

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“…There are other reports of K+-activated enzymes that recover activity only slowly on returning to potassium salts after prolonged dialysis against water ofnon-activation ions (Green, 1964;Wilson et al, 1967;Wampler & Westhead, 1968;Bothwell & Datta, 1971).…”

Section: Below)mentioning

confidence: 99%

Kinetic and spectroscopic evidence of cation-induced conformation changes in yeast K+-activated aldehyde dehydrogenase

Betts¹,

Poole²,

Springham³

et al. 1979

Biochemical Journal

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The activity, stability and spectroscopic properties of yeast K+ -activated aldehyde dehydrogenase were measured at various times after removal from, and after returning to a solution containing K+. Enzyme activity is rapidly lost on removal of most of the K+ and rapidly regained if K+ is replaced immediately. These activity changes are slower than likely rates of K+ dissociation and association. These rapid changes in concentration result in altered enzyme stability with enzyme in K+ the more stable. U.v. difference spectra are produced whenever enzyme in an activating environment (K+ or Tl+) is compared with enzyme in a non-activating environment (Tris+ or Li+). These spectral changes occur within 10s. The saturation characteristics with K+ are hyperbolic for all three phenomena of activation, stabilization and spectral change, with estimated apparent dissociation constants (Ks) for K+ of 7.5 mM, 5.5 mM and 6 mM respectively. Continued incubation of enzyme in the absence of K+ results in the accumulation of an enzyme form that re-activates only slowly on replacing K+. Stability characteristics in various concentrations of K+ over equivalent time scales are consistent with the existence of additional conformations. Spectroscopic evidence also indicates such additional slow conformation changes. Results have been interpreted in terms of two separate conformation transitions induced or stabilized by K+.

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The activation of l-threonine dehydrogenase by potassium ions

Cited by 13 publications

References 15 publications

Inhibition of monoamine oxidase by substituted hydrazines

Inhibition of monoamine oxidase by substituted hydrazines

Interactions of monoamine oxidase with substrates and inhibitors

Kinetic and spectroscopic evidence of cation-induced conformation changes in yeast K+-activated aldehyde dehydrogenase

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