Kinetic studies on inhibition of aminopropyltransferases by aurintricarboxylic acid in vitro

Activities of aminopropyltransferases (spermidine synthase and spermine synthase) were inhibited by aurintricarboxylic acid (ATA). Spermidine synthase was slightly more sensitive to the inhibitor than spermine synthase. These inhibitions were not prevented by 0.15 M NaCl. Inhibition by ATA of spermidine synthase was ‘uncompetitive’ with respect to putrescine and that of spermine synthase was ‘non-competitive’ with respect to spermidine. When the amount of spermidine synthase or spermine synthase was varied, inhibition ratio hardly changed on either case implying no appreciable interaction between ATA and these enzymes.