Polyamines as Endogenous Growth Regulators

Abstract

It is probable that all cells contain the diamine putrescine (Put; 1,4diaminobutane) and the triamine spermidine (Spd), while eukaryotic cells contain the tetramine spermine (Spm) as well (1, 8). In both prokaryotes and eukaryotes (54), including higher plants (13), mutants lacking the ability to biosynthesize polyamines (PAs) are unable to grow and develop normally (13, 54). Since the addition of PAs to these mutants generally restores normal growth and development, it is reasonable to conclude that PAs are essential to all cells. This conclusion is reinforced by the demonstrable effects of “suicide inhibitors” of the main PA-biosynthetic enzymes, ornithine decarboxylase (ODC) and arginine decarboxylase (ADC). These compounds, a-difluoromethylornithine (DFMO) and a-difluoromethylarginine (DFMA), specifically and irreversibly bind to and inhibit ODC and ADC, respectively. The ensuing decline in cellular PA titers is accompanied by a diminution or cessation of growth and development, which are restored upon the addition of the relevant PA.