ENHANCING EFFECT OF ZINC ACETATE ON THE BINDING OF 1-NITROPYRENE TO POLYDEOXYGUANYLIC-POLYDEOXYCYTIDYLIC ACID IN THE HYPOXANTHINE XANTHINE-OXIDASE SYSTEM

The main aim of this research was to investigate whether conformationa l alteration of polydeoxyguanylic-polydeoxycytidylic acid (poly[dG-dC] . poly[dG-dC]) by zinc acetate would have an effect on the binding of 1-nitropyrene(1-NP) to poly[dG-dC] poly[dG-dC]. The binding of 1-NP t o poly[dG-dC] . poly[dG-dC] in the hypoxanthine-xanthine oxidase syste m in vitro was increased by zinc acetate. This increase was abolished when EDTA was added to the preincubated mixture of poly[dG-dC] . poly[ dG-dC] and zinc ions. Neither the production of 1-aminopyrene and its expected intermediates, N-hydroxy-1-aminopyrene and 1-nitrosopyrene, n or the 1-NP remaining in the reaction mixture was altered by the addit ion of zinc acetate without poly[dG-dC] - poly[dG-dC]. From these find ings, it seems that the hypoxanthine-xanthine oxidase system is not ac tivated by zinc acetate. On the other hand, under the same reaction co nditions but the hypoxanthine-xanthine oxidase system and 1-NP, it has been reported that zinc ions or complexes transform the B-form of pol y[dG-dC] . poly[dG-dC] to the Z-form. Therefore, these findings indica te that the formation of the Z-form or intermediates from the B-form b y zinc ions may promote the binding of 1-NP to poly[dG-dC] . poly[dG-d C].