“…Generally, the steady-state levels of Spd and Spm are more tightly regulated than those of Put through transcriptional, translational, and posttranslational control mechanisms (for recent reviews, see Handa and Mattoo, 2010;Mattoo et al, 2010). However, the intracellular pool of free polyamines depends not only on the biosynthetic rate but also on several other processes, including transport, conjugation, and degradation (Persson, 2009;Alcázar et al, 2010;Angelini et al, 2010;.…”