Synthesis of New Polymer-Bound Adenine Nucleotides Using Starburst PAMAM Dendrimers

Two types of new polymer-bound adenine nucleotides were synthesized by coupling adenine nucleotides (ATP and ADP) with starburst polyamidoamine (PAMAM) dendrimers. The first type was obtained by coupling native adenine nucleotides directly with a carboxy-terminated PAMAM dendrimer. In the second type, the nucleotides were modified by introducing a spacer arm containing a carboxylic end group (N^6-RATP and N^6-R-ADP) and coupled with an amine-terminated PAMAM dendrimer. Both types of the dendrimers were coupled with native or the modified nucleotides using the well-known carbodiimide activation technique. The optimum coupling pH and temperature were 4 and 30 °C, respectively, for preparing the carboxy-terminated PAMAM-bound ATP or ADP, and were 9 and 50 °C, respectively, for preparing the amine-terminated PAMAM-bound A^6-R-ATP or A^6-R-ADP. The ATP or ADP contents in the synthesized polymers were found to be 4 mol of ATP or of ADP/mol of carboxyterminated PAMAM-bound ATP or ADP and 25 mol of ATP or ofADP/mol of amineterminated PAMAM-bound A^6-R-ATP or A^6-R-ADP. The coenzymatic activities relative to the native ATP of the carboxy-terminated PAMAM-bound ATP against glucokinase and hexokinase were 16 and 7%, respectively, and those of the amine-terminated PAMAM-bound A^6-R-ATP 2 and 1%, respectively. The coenzymatic activities relative to the native ADP of the carboxy-terminated PAMAM-bound ADP and the amineterminated PAMAM-bound N^6-R-ADP against acetate kinase were 24 and 3.5%, respectively.