PLANT PHYSIOLOGY , Vol 113, Issue 2 387-395, Copyright © 1997 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
Polyamines and Pectins (I. Ion Exchange and Selectivity)
J. Messiaen, P. Cambier and P. Van Cutsem
Facultes Universitaires Notre-Dame de la Paix, Laboratoire de Biotechnologie Theorique, 61 Rue de Bruxelles, B-5000 Namur, Belgium
The ion-binding and -exchange properties of putrescine, spermidine, and
spermine on purified walls of carrot (Daucus carota L.) cell suspensions
were investigated by producing ion-exchange isotherms and comparing them
with the behavior of Na+, Mg2+, and Ca2+. The cation exchange capacity of
the carrot cell walls was 0.8 equivalent kg-1 dry matter, and the ionic
selectivity sequence of the walls for polyamines followed the sequence
spermine4+ > spermidine3+ [almost equal to] Ca2+ > putrescine2+. The
polyamines were subjected to only electroselectivity and probably did not
induce any favorable supramolecular conformation of pectin like the one
induced by Ca2+. Triangular ion exchanges were also performed with three
diamines: ethanediamine, butanediamine, and octanediamine. The shorter the
diamine, the higher the total adsorption and selectivity of the exchange.
The lower selectivity of the cell wall for putrescine was partly attributed
to its inability to access and displace Ca2+ from higher affinity sites
within dimerized pectic sequences. The polyamine adsorption and exchange on
pectic sequences could result in pectic signal modulation in pathogenesis
and in differentiation.
