DETERMINATION OF THE SUPEROXIDE DISMUTASE-LIKE ACTIVITY OF CIMETIDINE-CU(II) COMPLEXES

Using the direct method of pulse radiolysis to determine the superoxide dismutase like activity of copper(II) cimetidine complexes, it was found that the reaction rate constant with O-2, kcat, was (8.5 ± 0.5) × 108 M-1s-1 independent of the cimetidine concentrations present in excess of 50-200 μM over the metal. The results suggest that either the 1: 1 ligand to metal complex does not catalyze O-2 dismutation at a comparable rate to that of the 2: 1 complex, or that the stability constant of the last species is much higher than that determined earlier by Kimura el al.,1 and only the 2: 1 species is present in the solutions. With the indirect methods of cytochrome c and NBT for determining the ability of these complexes to catalyze O-2 dismutation, these compounds exhibited a much lower SOD activity. and kcat was determined to be (5.0 ± 0.3) × 106 and (7.± 0.4) × 101 M-1s-1. respectively using the two assays. © 1991 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.