Putrescine aminopropyltransferase

Putrescine aminopropyltransferase (spermidine synthase EC. 2.5.1.16) was first purified from E. coli and shown to carry out the synthesis of spermidine and MTA from putrescine and dSAM (Bowman et al., 1973). More recently, spermidine synthase and spermidine aminopropyltransferase (spermine synthase) have been separated and purified to homogeneity from several mammalian sources (Pajula et al., 1979 Samejima and Yamanoha, 1982 Raina et al.,... 

Aminopeptidase, cytosol Aminopeptidase, leucine Aminopropyltransferase, putrescine Aminotransferase Aminotransferase, alanine Aminotransferase, aspartate Aminotransferase, glutamate-glyoxylate Aminotransferase, ornithine-keto acid Aminotransferase, serine-glyoxylate Ammonia... 

This scant information about aminopropyltransferases is due in part to the difficulty of measuring their activities, since one of the precursors, dSAM, is unstable and not easily available. Although its synthesis has been improved, an extinction coefficient has not been published (Samejima et al., 1978). We have developed a method for the evaluation of spermidine synthase in oat leaves (Tiburcio et al., 1986a) by a coupled reaction without using dSAM. We add SAM, [ ] putrescine, and pyridoxal phosphate to the assay mixture. Incorporation of the label into spermidine can be detected after 45 min of incubation at 37 C. Labeled spermidine is separated from labeled putrescine or spermine by elution with HCl in Dowex 50 W-H" " columns (Tiburcio et al., 1986a). A similar procedure can be used for the evaluation of spermine synthase (A. F. Tiburcio et al., unpublished observations). 

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