Does a Ferruginous Peroxidase Catalyze the Oxidative Decomposition of Safflor Yellow B?

Abstract

Summary Protein extracts from dyer's saffron (Carthamus tinctorius) seedlings catalyzed the oxidative decomposition of safflor yellow B (SFLY-B) pigment. The catalytically active fraction was isolated and purified up to about 85-fold through (NH4)2SO4 precipitation, Sephadex G-100 gel filtration, and isoelectric focusing. Under aerobic conditions, the purified enzyme oxidized the pigment positively whether exogenous H2O2 was present or not. Its pH optimum was 8.0 in Tris/HCl buffer. Various effects were detected in the buffers used: phosphate, borate, maleate, and glycine acted on the enzyme unfavourably. Externally supplied O2 enhanced the SFLY-B decomposition. H2O2 stimulated the reaction, and the effect was promoted synergistically through flushing O2 gas. At 25 µM level, Fe(II) inhibits the activity. Mn(II) promotes the enzyme activity, whereas Fe(III) was not as effective as previously expected. The enzyme reaction was influenced by various inhibitors. Among those tested at 1 mM, o-phenylenediamine dihydrochloride, sodium diethyldithiocarbamate, KCN, EDTA, and KAg(CN)2 exhibited strong toxicities. α,α′-Dipyridyl, CH2ICO2NH2, NaF, and o-phenanthroline promoted the reaction. The results are compared with those from observations of the catalytic properties and the electrophoretic pattern of a commercial sample of horseradish peroxidase (EC 1.11.1.7).