Polyamine Transport in Aspergillus nidulans

Abstract

The uptake of putrescine, spermidine and spermine was studied in A. nidulans using 14C-labeled polyamines. Active transport systems, inhibited by azide and regulated by N availability, exist at least for putrescine and spermidine. Putrescine is taken up 2-3 times more rapidly than spermidine, reflecting a lower Km for the former substrate. The 2 uptake systems appear to be independent, spermidine uptake being inhibited by putrescine and spermine, while putrescine uptake is not inhibited by the other 2 polyamines. The relationships of these transport systems to the 10-fold or greater difference between spermidine and putrescine concentrations required to support growth of the putrescine auxotroph are discussed.