The biosynthesis of spermidine and spermine from putrescine and methionine.

Putrescine, NHz(CH&NHZ, spermidine, NHz(CH&NH(CH&NHt, and sperminc, NH2(CH&NH(CH&NH(CH&NHt, are naturally occurring polyamines (for bibliography see ref. 6). That they have physiological significance is suggested by the following: they have been shown to be essential growth factors for Hemophilus injluenza (7-9) and for a mutant of Aspergillus nidulam (lo), and to stimulate the growth of Lactobacillus casei (ll), Neisseria per$ava (12) and Pasteurella tularensis (13). A wide distribution has been reported for spermine in animal tissues and for putrescine in microorganisms, and recent studies have shown that spermidine is also present in many mammalian and bacterial cells, often attaining concentrations of 100 to 300 pgrams/gm. of wet weight (6, 8, 14). Studies from this laboratory (unpublished) and by Keister (15) have demonstrated that spermidine and spermine have a high affinity for nucleic acids. Recently, Escherichia coli bacteriophage T4 has been shown to contain a concentration of putrescine and spermidine sufficiently high to neutralize a large part of the bacteriophage nucleic acids (16). Pharmacological studies have demonstrated that spermine has a potent nephrotoxic action, producing death from renal tubular necrosis in laboratory animals (17-19) ; furthermore, under certain conditions spermine and spermidine, or their enzymatic degradation products, are highly toxic to bacteria (19-25), trypanosomes, and spermatozoa (19). Spermine and spermidine have also been shown to antagonize the bacteriostatic action of quinacrine, quinine, and diamidines (23-26). Until recently (l-5), however, very little has been reported concerning the biosynthesis of spermidine and spermine. In the work reported in this paper we have demonstrated that isotopitally labeled putrescine was incorporated into these polyamines in several microorganisms. With growing cultures of E. coli and of A. nidulans we have shown by the use of doubly labeled CY-N15-putrescine that the putrescine was incorporated as a unit into these polyamines without significant change in the Cl4 to Nr5 ratio. These data indicated that putrescine is the source of the diaminobutane moiety in spermidine and spermine. The source of the terminal aminopropane moiety of these compounds has been shown by other work from this laboratory by Greene (2, 4), which demonstrated that the isotope from 2-c14-DLmethionine was incorporated into spermidine in cultures of Neurospora crassa. In this report the biosynthesis of spermidine has also been demonstrated in cell-free preparations of E. co& and the reaction