Abstract
When the concentration of aminopyrine, [AMP], was greater than that of peroxyphenylacetic acid, [PPAA], the reaction of PPAA with AMP in the absence of catalase at pH 4.5 showed the electron spin resonance (ESR) spectrum of the aminopyrine cation radical (1), whereas that at pH 6.8 did not. On the other hand, when [AMP]⪈[PPAA], a new ESR spectrum (g=2.0053, A1=16.9 (1N), A2=14.5G (6H) which was entirely different from that of 1 was obtained at both pH 4.5 and 6.8. Spin-trapping experiments suggested that the new spectrum was derived from the phenylacetyl radical-adduct of AMP (2). In the presence of catalase, when [AMP]>[PPAA], the reaction of PPAA with AMP showed the ESR spectrum of 1 even at pH 6.8. The amount of benzyl alcohol formed was decreased in the presence of catalase in comparison with that in the absence of catalase. These results suggest that homolytic oxygen-oxygen bond cleavage and oxy radicals generated play no major role in the PPAA-supported oxidation of AMP by catalase.
