Ornithine Decarboxylase and S-Adenosyl Methionine Decarboxylase in Skin Fibroblasts of Normal and Cystic Fibrosis Patients

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Abstract
Summary: The key enzymes in the synthesis of the naturally occurring polyamines, ornithine decarboxylase (ODC) and S-adenosyl methionine (SAM) decarboxylase, were investigated during cell growth and aging in fihroblast cultures from normal patients and patients with cystic fibrosis. A linear correlation between increased S-adenosyl methionine activity and putrescine concentration was apparent in all cell lines. A putrescine concentration of 0.8 mM was optimal for enhancement of SAM decarboxylase activity. The passage number of the cell line correlated inversely with maximal putrescine-stimulated SAM decarboxylase activity, earlier passage numbers having the highest specific activity (Fig. 1 ) No significant differences in basal or putrescine-stimulated SAM decarboxylase activity were noted between normal fihrohlast cultures and cells from patients with cystic fibrosis (Fig. 2). SAM decarboxylase activity increased as the cell lines approached confluence. Activity was lowest during exponential growth (Fig. 3). ODC activity was increased during early exponential growth and fell as cells reached confluence (Fig. 4). No differences in ODC activity and putrescine inhibition between the normal and cystic fibrosis cell cultures at equivalent points of exponential growth were noted. Speculation: Although there are definite alterations of polyamine levels in patients with cystic fibrosis, no abnormalities in ornilhine decarboxylase or S-adenosyl methionine decarboxylase were found in cystic fibroblasts (Fig. 5). Differences in polyamine biosynthetic activity appeared to be a function of cell age. Therefore, it is postulated that polyamine abnormalities in cystic fibrosis are caused by enzymes other than SAM or ornithine decarboxylase. The polyamine abnormalities may relate to abnormalities in the metabolism of polyamines (e.g., acetylation or catabolism) or be a consequence of increased in vivo synthesis secondary to humoral factors which have not yet been identified.

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