DEGRADATION OF CHLOROPHYLL BY NITROGEN-DIOXIDE GENERATED FROM NITRITEBY THE PEROXIDASE REACTION

Nitrite, but not nitrate, added to a mixture containing horseradish pe roxidase (HRP) and H2O2, bleached chlorophyll (Chl). The optimum pH fo r Chl bleaching was 4.0. Ascorbate, p-hydroxyphenyl acetate (HPAA), gl ycyltyrosine (Gly-Tyr) and amines such as morpholine and diethylamine inhibited Chl bleaching. The reaction products from HPAA and Gly-Tyr s howed an absorption peak at 438 nm in an alkaline solution. The laser- Raman spectrum of the product from HPAA showed a band at 1336 cm(-1) i dentical to that of authentic 2-nitrotyrosine, These results indicated the formation of nitrogen dioxide, the one-electron oxidation product of nitrite, which caused Chl bleaching in the nitrite/H2O2/HRP system . Nitrite caused neither inhibition of the ascorbate peroxidase reacti on nor Chl bleaching with the H2O2/ascorbate peroxidase system.