the observed relationships among intracellular levels of labeled putrescine , polyamines , and protein bound hypusine after growth of cells with the various labeled amines and with or without an inhibitor of polyamine biosynthesis supply evidence that spermidine is the immediate amine precursor of hypusine and that the 4-amino-2-hydroxybutyl portion of hypusine derives from the butylamine moiety of spermidine .
C0032433
polyamines
C0002508
amine