Cycloheximide induced in vivo modification of ornithine decarboxylase in <i>Physarum polycephalum</i>

Mitchell, John L.A.; Sedory, M.J.

doi:10.1016/0014-5793(74)80646-0

Cited by 15 publications

(6 citation statements)

References 12 publications

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“…Thus the activity fluctuations reported previously [7] in response to cycloheximide, were due to this interconversion between the low K M (active) and high K M (inactive) enzyme forms, which produced a dramatic variation in the overall K M for PLP when measured at intermediate coenzyme levels.…”

Section: Discussionmentioning

confidence: 73%

“…The interconversion of the Physarum ornithine decarboxylase forms, which also appears to involve a posttranslational modification, allows the regulation of form II, and since this form has the greatest affinity for coenzyme, enzyme activity. Thus the activity fluctuations reported previously [7] in response to cycloheximide, were due to this interconversion between the low K M (active) and high K M (inactive) enzyme forms, which produced a dramatic variation in the overall K M for PLP when measured at intermediate coenzyme levels.…”

Section: Discussionmentioning

confidence: 73%

“…Since cycloheximide and actinomycin D block this stimulation, and frequently cause a rapid loss in existing activity, it is thought that the mechanism of control of this apparently labile enzyme is through the regulation of its synthesis and degradation [3][4][5][6]. Recently, however, Mitchell and Sedory [7] presented evidence suggesting that the rapid fluctuations in the ornithine decarboxylase activity of Physarum, which had been exposed to cycloheximide, were in a large part due to variations in the ability of this enzyme to be activated by its coenzyme, pyridoxal 5'-phosphate (PLP). Regulation by such an enzyme modification is in agreement with the accumulating evidence for at least partial control of this enzyme by post-transcriptional mechanisms [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

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Multiple ornithine decarboxylase forms in Physarum polycephalum: Interconversion induced by cycloheximide

1976

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Section: Discussionmentioning

confidence: 73%

Section: Discussionmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

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Multiple ornithine decarboxylase forms in Physarum polycephalum: Interconversion induced by cycloheximide

1976

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“…They include (a) enzyme stabilization by a metabolite building up after inhibition of RNA or protein synthesis (4) and (b) inhibitor-induced changes in a small protein factor that modifies enzyme activity (22). We are continuing to investigate those and other possibilities.…”

Section: Discussionmentioning

confidence: 99%

Effects of Inhibitors of RNA and Protein Synthesis on Aspartate Transcarbamylase Activity in Etiolated Plant Tissue

Johnson¹,

Niblett²,

Lee³

1976

Plant Physiol.

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Aspartate transcarbamylase (ATCase) activity declines in etiolated cowpea (Vigna unguiculata L. Waip.) and soybean (Glycine max L. Merr.) hypocotyls between 3 and 11 days after planting. Treating cowpea hypocotyls with cydobeximide (CH), actinomycin D (AMD), 6-methyl purine (6-MP), or cordycepin increases ATCase activity up to 740, 350, 465, and 305%, respectively, over water-treated controls 48 to 72 hours after treatment. In contrast erythromycin had no effect, and D-threo-chloramphenicol (CHL) ATCase2 (25). In higher plants, ATCase involvement in pyrimidine regulation is not established, although it likely has a regulatory role because the enzyme from several plant species is UMPsensitive in vitro (1,14,23,26,33). ATCase activity increases during times of enhanced nucleic acid synthesis, including seed germination (21), response to 2,4-D (14), and after virus infection (24).In higher plants, ATCase activity is elevated in young tissue and decreases as tissue matures (14,24,30 (14).Inhibitors were applied to seedlings uprooted 7 to 8 days after planting, after roots were excised underwater at the hypocotylroot juncture. Hypocotyls were immersed in sets of five into the proper solutions, placed in a vacuum desiccator, and a vacuum was drawn for 3 min, and then slowly released. Control hypocotyls were immersed in H20 and treated comparably. The five seedlings of each set were then placed with their bases in a test tube (18 x 150 mm) containing 5 ml of 20 mm K-phosphate buffer, pH 5.6. Test tube tops were sealed with Parafilm around the emerging epicotyls, and the tubes were returned to the dark at 29 to 30 C. Five seedlings were used per sample, and duplicate samples were used for each treatment. All operations were in dim light. At harvest, the basal cm of each hypocotyl was discarded, and the next 11 cm were weighed, coarsely diced, and frozen until extracted.Hypocotyl Extraction. Hypocotyl sections were homogenized for 15 sec with a Willems Polytron PT 20 ST, with the speed control at five. Homogenization was in 2 ml of cold 0.1 M ethanolamine-HCl buffei, pH 10 for cowpea and pH 9.5 for soybean, per g fresh weight in 50-ml centrifuge tubes kept in ice H20. Samples were centrifuged 15 min at 37,000g and 3 C.Aliquots of the supernatant were frozen for later analysis of RNA and buffer-soluble protein, and the remainder was dialyzed for 16

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“…This model, valid, probably, for a narrow range of cycloheximide concentration in a given system, could explain the increase of the de novo synthesis of an enzyme molecule under conditions entailing inhibition of the synthesis of most cellular proteins. The question whether this is true for the increase of uridine kinase following cycloheximide, or whether we are dealing with an impaired enzyme degradation or, eventually, with the enhancement of activity of pre-existing enzyme or the enzyme modification in response to cycloheximide [35] contitutes the subject of our further studies.…”

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confidence: 99%

Character of the Stimulatory Response of Uridine Kinase in Rat Livers to Cycloheximide Treatment

Čihák

1975

European Journal of Biochemistry

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Administration of cycloheximide to adult rats resulted in the enhancement of uridine kinase activity in the liver. The increase of enzyme activity was not affected by adrenal secretion or uptake of food. Actinomycin D, hydroxyurea and puromycin injected simultaneously with cycloheximide depressed the increase of enzyme activity. On the contrary, administration of 5-azacytidine following cycloheximide resulted in further enhancement of uridine kinase. While the half-time of template RNA for uridine kinase in control rat livers was 24 h, for cycloheximide-stimulated enzyme it was about 11 h. At higher dose levels cycloheximide leads to an increased incorporation of both uridine and orotic acid into liver RNA; however, this effect was not observed in the starved animals. The mechanism of action of cycloheximide is briefly mentioned.

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Cycloheximide induced in vivo modification of ornithine decarboxylase in Physarum polycephalum

Cited by 15 publications

References 12 publications

Multiple ornithine decarboxylase forms in Physarum polycephalum: Interconversion induced by cycloheximide

Multiple ornithine decarboxylase forms in Physarum polycephalum: Interconversion induced by cycloheximide

Effects of Inhibitors of RNA and Protein Synthesis on Aspartate Transcarbamylase Activity in Etiolated Plant Tissue

Character of the Stimulatory Response of Uridine Kinase in Rat Livers to Cycloheximide Treatment

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