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- The induction of an IAA-destroying enzyme in Arthrobacter sp.that can utilize IAA as its sole source of carbon and nitrogenwas investigated.
- 1. The enzyme was most effectively inducedby 103 to2x103 M IAA, at pH 6.5.
- 2. All testedIAA analogs were unable to induce the enzyme.Analogs otherthan indole-3-lactic acid were rather inhibitoryon the inductionwith IAA.
- 3. The induction period was shortened with the ageof culturein both polypeptone and acetate media.
- 4. Pretreatmentof the bacterium with IAA caused a shorteningof the inductionperiod.
- 5. The induction was inhibited by various antibiotics,aminoacid analogs and nucleobase analogs.
- 6. The inductionwas less remarkable in actively proliferatingcells than itwas in slowly proliferating ones.
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- Some properties of the IAA-oxidizing activity of lyophilizedcells of Artkrobacter sp. were examined.
- 1. IAA oxidationseems not to be catalysed by peroxidase, polyphenoloxidase,laccase or dehydrogenase, but by an oxidase systemdifferentfrom the one reported earlier.
- 2. The optimal pH for the oxidizingsystem is ca. 6.0, and thesystem is comparatively stable atpH 5 to 10.
- 3. The optimal substrate (IAA) level is 103M.
- 4. Activity is inhibited by metal-chelating reagents, suchassodium azide, potassium cyanide, sodium diethyldithiocarbamate,potassium xanthogenate and 8-hydroxyquinoline, and sulfhydrylreagents, such as iodoacetamide, monofluoroacetic acid, p-chloromercuribenzoate,isatin, ß-naphthoquinone and ß-naphthoquinone-4-sulfonate.Hydroxybenzoic acid, sulfosalicylic acid and 2,4-dichlorophenolare also inhibitory.
- 5. None of the IAA analogs tested (indole,skatole, 2,3-dihydroxyindole,indole-3-aldehyde, -3-carboxylicacid, -3-propionic acid, -3-lacticacid, -3-butyric acid, 5-hydroxyindole-3-aceticacid and D,L-tryptophan) are oxidized by the cells, and someanalogs (indole-3-carboxylicacid, -3-propionic acid, -3-butyricacid, 5-hydroxyindole-3-aceticacid, naphthalene-acetic acidand 2,4-D) are inhibitory at comparativelyhigh concentrations.
- 6. The oxidizing activity is not stimulated by Mn++ and isinhibitedby Co++, Cu++ and Hg++.
- 7. The oxidizing activitydisappears completely within 6 hrat 30, but is kept unchangedat least for two weeks at 20.
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