ISOLATION AND CHARACTERIZATION OF 2 PHLOROGLUCINOL OXIDASES FROM CABBAGE (BRASSICA-OLERACEA L)

Two isozymes (F-IB and F-II) of phloroglucinol oxidase (PhO) in cabbag e (Brassica oleracea L.) were purified from cabbage. The purified enzy mes were found to be in a homogeneous state by polyacrylamide gel elec trophoresis (PAGE) and sodium dodecyl sulfate (SDS)-PAGE. The molecula r weights of F-IB and F-II were estimated to be similar to 43 000 and 32 000, respectively, by SDS-PAGE. Both purified enzymes only oxidized 1,3,5-trihydroxybenzenes, such as phloroglucinol and phloroglucinolca rboxylic acid. Both enzymes also had strong peroxidase (POD) activity. The pH optima of PhO and POD of F-IB were 8.0 and 6.7, respectively, and those of F-II were 7.4 and 6.7, respectively. Activities of both F -IB and F-II were stable in the pH range 6-11 at 5 degrees C for 20 h, and were markedly inhibited by sodium diethyldithiocarbamate and pota ssium cyanide. MnCl2 markedly activated the PhO activity of F-LB and F -II, but strongly inhibited their POD activity.