On the mechanism of aconitase.

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Publication Type thesis
School or College School of Medicine
Department Biochemistry
Author Speyer, Joseph Frederick
Title On the mechanism of aconitase.
Date 1954
Description Analysis of aconitase kinetics shows that all three substrates, citrate, d(+)-isocitrate, and cis aconitate, are equivalent in the number of slow, rate determining steps in their inter-conversion. Kinetics and the inhibition studies using deuterium oxide indicate that cis aconitate is not an obligatory intermediate in the citrate: isocitrate conversion. The lack of deuterium incorporation from the medium into enzymatically formed citrate from isocitrate shows that conversion to involve and intramolecular hydrogen rearrangement and eliminates cis aconitate as the intermediate. The proposed mechanism is similar to known intramolecular hydrogen rearrangements, the Whitmore Shift of carbonium ions; It is though that the enzyme can induce carbonium ion formation in the substrate with the aid of ferrous iron. It is postulated that the metal serves as an electron acceptor or Lewis acid, and that the carbonium ion is formed as a result of coordination of the hydroxyl with the metal. The postulated mechanism accounts for all the reactions of he enzyme and for its kinetic behavior. Aconitase has been prepared from mitochondria by freezing and thawing. The soluble aconitase is more active than the mitochondrial enzyme in the isocitrate-aconitate and citrate-aconitate reactions, but mitochondrial aconitase is more active in the isocitrate-citrate transformation. Soluble aconitase showed an optimum at pH 7.3 but mitochondrial aconitase showed optima at pH 5.8 and 7.3. The isocitrate-aconitate and citrate-aconitate reactions of both soluble and mitochondrial aconitase were inhibited by o-phenanthroline and reactivated by ferrous ions plus ascorbate. Mitochondria incubated with isocitrate retain aconitate. The data on the intracellular distribution of aconitase were markedly affected by the condition of the assay.
Type Text
Publisher University of Utah
Subject Metabolism; Mitochondrial
Subject MESH Aconitate Hydratase; Enzymes
Dissertation Institution University of Utah
Dissertation Name PhD
Language eng
Relation is Version of Digital reproduction of "On the mechanism of aconitase." Spencer S. Eccles Health Sciences Library. Print version of "On the mechanism of aconitase." available at J. Willard Marriott Library Special Collection. QP6.5 1954 .S64.
Rights Management © Joseph Frederick Speyer.
Format Medium application/pdf
Identifier us-etd2,4419
Source Original: University of Utah Spencer S. Eccles Health Sciences Library (no longer available).
ARK ark:/87278/s65b0h5z
Setname ir_etd
ID 194094
Reference URL https://collections.lib.utah.edu/ark:/87278/s65b0h5z
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