File Name : figs1.tif Caption : figure s1. general pathways of polyamines biosynthesis. most organisms use arginase to transform l-arginine to putrescine. an alternative pathway uses arginine decarboxylase to convert l-arginine into agmatine, which can be converted either directly or indirectly to putrescine. putrescine can be then further processed to yield spermidine and spermine. interaction with the s-adenosylmethionine pathway in the synthesis of spermidine and spermine is not shown.