Purification and characterization of some metabolic effects of S-neplanocylmethionine.
Our laboratory has previously demonstrated that treatment of mouse L929 cells with 1 microM 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 describes 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 microM (S-adenosylmethionine = 10 microM). 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.
D000241:Adenosine / Q000031:analogs & derivatives / Q000302:isolation & purification / Q000378:metabolism; D012437:Adenosylmethionine Decarboxylase / Q000378:metabolism; D000818:Animals; D004926:Escherichia coli / Q000201:enzymology; D007700:Kinetics; D007739:L Cells; D008297:Male; D008715:Methionine / Q000031:analogs & derivatives / Q000302:isolation & purification / Q000378:metabolism; D008745:Methylation; D008780:Methyltransferases / Q000037:antagonists & inhibitors; D051379:Mice; D051381:Rats; D012436:S-Adenosylmethionine / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000378:metabolism; D013379:Substrate Specificity
C031096:neplanocin A; D012436:S-Adenosylmethionine; C041100:S-neplanocylmethionine; D008715:Methionine; D008780:Methyltransferases; D012437:Adenosylmethionine Decarboxylase; D000241:Adenosine