Multiple ornithine decarboxylase forms in <i>Physarum polycephalum</i>: Interconversion induced by cycloheximide

Mitchell, John L.A.; Campbell, Harold A.; Carter, David D.

doi:10.1016/0014-5793(76)80010-5

Cited by 28 publications

(11 citation statements)

References 21 publications

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“…The quantitation of ornithine decarboxylase activity by capturing ['4C]C02 released from [l-'4C]ornithine has been previously described [12]. The actual components of the assay mixture varied somewhat with the experiment and are appropriately detailed in the figure legends.…”

Section: Assay Of Ornithine Decarboxylasementioning

confidence: 99%

“…Distinction between the activity attributed to the A and B forms of this enzyme was based on their differing affinities for coenzyme as described previously [12,13,16]. Both forms of this enzyme appear to have the same turnover number and pH optimum (pH 7.8) when assayed as described above in substrate concentrations of 1.0 mM or greater.…”

Section: Assay Of Ornithine Decarboxylasementioning

confidence: 99%

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Control of Ornithine Decarboxylase Activity in Physarum by Polyamines

Mitchell

Carter

Rybski

1978

European Journal of Biochemistry

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The addition of putrescine, spermidine, or spermine, to cultures of Physarum p~I y c e~h a / u m rapidly reduced the activity of ornithine decarboxylase, with maximal inhibition, 80 -90 %, occurring after 90 min. This response was not due to a decrease in enzyme molecules, but rather to the rapid conversion of the active enzyme to a stable, catalytically less active form. This response to exogenous polyamines was not accompanied by the appearance of a macromolecular inhibitor (antizyme) either free, or bound to the enzyme. Physiological levels of the polyamines were also found to inhibit this enzyme in vitro both competitively and non-competitively, and to promote complete yet reversible inactivation of this enzyme in the absence of reducing agents. The data suggest that the control of this enzyme by endogenous polyamine levels may be distinct from its response to exogenous polyamines.

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Section: Assay Of Ornithine Decarboxylasementioning

confidence: 99%

Section: Assay Of Ornithine Decarboxylasementioning

confidence: 99%

Control of Ornithine Decarboxylase Activity in Physarum by Polyamines

Mitchell

Carter

Rybski

1978

European Journal of Biochemistry

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“…h -s, in the presence of 1 mM spermidine. Ratl~er, the induction of DFMO insensitivity appeared to be directly related to the conversion of A-form enzyme to the B-form since the elevation of media osmolarity (following [6]) or the addition of cyclohexirnide [7] also immediately blocked enzyme sensitivity to DFMO (not shown).…”

Section: Resultsmentioning

confidence: 95%

“…In this latter, primitive eukaryotic system, the ornithine decarboxylase-modulating protein is stimulated by polyamines to modify this enzyme such that its affinity for the obligate coenzyme, pyridoxal 5'-phosphate (PLP), is severely diminished. Thus, even though total ornithine decarboxylase protein is rather stable in Physarum, it is rapidly and reversibly converted between the normal (A-form) and modified (B-form) states in response to external polyamines [5], altered media osmolarity [6], protein synthesis inhibitors [7], and normal progression through the mitotic cycle [8].…”

Section: Introductionmentioning

confidence: 99%

Selective inactivation of Physarum A‐form ornithine decarboxylase by α‐difluoromethylornithine

1981

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“…Furthermore the reabsorption of the released polyamine would not be fast enough to produce the observed rapid return to initial enzyme activity levels. It is more likely that exogenous polyamines [8] and osmotic shock, as well as the presence of inhibitors [9] and variations in growth and development [4,10], are all separate factors capable of influencing the common mechanism responsible for posttranslational activation and inactivation of ODC.…”

Section: Discussionmentioning

confidence: 99%