Abstract
The metabolic fate of putrescine labelled in vivo was investigated after administration of a trace (10 −7 M) of L-[ 14C]ornithine to exponentially growing mycelia of Neurospora crassa , followed by a large chase (2 mM) of L-[ 12C]ornithine. The specific radioactivities of putrescine and spermidine were determined during the chase period by reaction with [ 3H]dansyl chloride of known specific radioactivity and isolation of the dansyl-derivatives by thin-layer chromatography. Radioactivity remained in the putrescine pool for over 2 h during the chase period. This suggests that putrescine is largely sequestered (80% or more) in vivo . The metabolic sequestration of polyamines may be a significant factor in the regulation of polyamine synthesis.
Highlights
Radioactivity remained in the putrescine pool for over 2 h during the chase period
The extractable putrescine pool is about one-sixteenth the size of the spermidine plus spermine pools, and little increase is seen upon addition of ornithine in the chase period [5]
Panel A: Spennidine specific radioactivity observed during chase periodr0); the dashed line represents the theoretical result based on a doubling time of 163 min and the premise that no further radioactivity enters spermidine
Summary
Radioactivity remained in the putrescine pool for over 2 h during the chase period. This suggests that putrescine is largely sequestered (80% or more) in vivo. The specific radioactivity of ornithine in the original perchloric acid extract was deter mined as previously described [8]. The specific radioactivity of newly synthesized polyamine
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