Polyamine Pools and the Control of Ornithine Decarboxylase Activity
The metabolism of the polyamines, putrescine, spermidine and spermine is represented in a general way in Fig. 1. During growth, the polyamines are formed from ornithine (and in many species, arginine) and S-adenosylmethionine. The resulting pools of polyamines, in addition to fulfilling the needs of an expanding cell mass, are potentially excreted, sequestered by cell constituents and interconverted or catabolized. The regulation of polyamine biosynthesis is exerted in part by the polyamines themselves and also by signals related to the onset or continuation of the cell cycle and differentiation. In relation to the former signal, polyamines rarely, if ever, exert significant feedback inhibition in the strict sense on their own synthesis. Alternative mechanisms, however, have come to light, among which are the modification, antizyme inhibition and elimination of the ornithine decarboxylase (ODC) protein in response to excess polyamines (Pegg and McCann, 1982; Tabor and Tabor, 1984, 1985).
KeywordsOrnithine Decarboxylase Neurospora Crassa Polyamine Metabolism Ornithine Decarboxylase Activity Polyamine Pool
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