Spermidine and spermine interfere with in vitro BAPNA-mediated proteolyticactivity in organogenic tobacco thin layers

The effect of different concentrations of putrescine, spermidine and spermi ne on proteolytic activity was tested in tobacco thin layers cultured for 1 5 days under vegetative bud-inducing conditions (indoleacetic acid, IAA plu s benzyladenine, BA). Two artificial substrates were used for the proteolyt ic assay: azocasein and BAPNA. With the former substrate, both under low or high ionic strength conditions, exogenous polyamines had no effect, indepe ndently of the polyamine or the concentration used. With the latter substra te, spermidine and spermine at the highest concentrations strongly reduced protease activity, confirming that these long, flexible molecules affect bi ological activities. This behaviour is discussed in relation to pH, ionic s trength, and number of charged groups/length of the molecule.