Purification and characterization of some metabolic effects of S-neplanocylmethionine

B. T. Keller, R. S. Clark, A. E. Pegg, R. T. Borchardt

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14 Scopus citations

Abstract

Our laboratory has previously demonstrated that treatment of mouse L929 cells with 1 μM neplanocin A results in the metabolic formation of S-neplanocylmethionine (Keller, B.T., and R.T. Borchardt, Biochem. Biophys. Res. Commun. 120:131-137 (1984)). The present study described an efficient procedure for the purification of this analog from L cells based on its inherent chemical stability in alkaline conditions. Several metabolic effects of S-neplanocylmethionine are also reported. In L cells, S-neplanocylmethionine was determined to have an apparent half-life of 13 hr compared to 1 hr for S-adenosylmethionine during the initial 2 hr of a cycloleucine block. Analysis of polyamine levels in neplanocin A-treated cells showed a 3.8-fold decrease in putrescine and a 1.7-fold decrease in spermidine by 24 hr, reflecting a decrease in the cell growth rate in response to neplanocin A rather than a direct effect of S-neplanocylmethionine on the cellular S-adenosylmethionine decarboxylase. Consistent with these results are our findings that S-neplanocylmethionine does not significantly inhibit purified rat prostate or Escherichia coli S-adenosylmethionine decarboxylase and that [carboxy-14C]S-neplanocylmethionine exhibits no substrate activity with either enzyme. Purified S-neplanocylmethionine was observed to be a weak inhibitor of both S-adenosylmethionine-dependent protein carboxymethyltransferase and lipid methyltransferase in L cell extracts, having an IC50 value of 205 μM (S-adenosylmethionine = 10 μM). Similar studies with [methyl-3H]S-neplanocylmethionine indicate that the analog has little substrate activity in these two L cell methylation reactions and thus appears to act as a poor competitive inhibitor.

Original languageEnglish (US)
Pages (from-to)364-370
Number of pages7
JournalMolecular pharmacology
Volume28
Issue number4
StatePublished - 1985

All Science Journal Classification (ASJC) codes

  • Molecular Medicine
  • Pharmacology

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