Isolation and Characterization of Two Phloroglucinol Oxidases from Cabbage (BrassicaoleraceaL.)

Abstract

Two isozymes (F-IB and F-II) of phloroglucinol oxidase (PhO) in cabbage (Brassica oleracea L.) were purified from cabbage. The purified enzymes were found to be in a homogeneous state by polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate (SDS)-PAGE. The molecular weights of F-IB and F-II were estimated to be ∼43 000 and 32 000, respectively, by SDS-PAGE. Both purified enzymes only oxidized 1,3,5-trihydroxybenzenes, such as phloroglucinol and phloroglucinolcarboxylic 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 °C for 20 h, and were markedly inhibited by sodium diethyldithiocarbamate and potassium cyanide. MnCl2 markedly activated the PhO activity of F-IB and F-II, but strongly inhibited their POD activity. Keywords: Cabbage (Brassica oleracea L.); polyphenol oxidase; phloroglucinol oxidase; peroxidase; characterization

Cantaloupe melon peroxidase: Characterization and effects of additives on activity

“…The inhibitory effect of Mn 2+ , and the ineffectiveness of both metal chelating EDTA and singlet oxygen scavenger, superoxide dismutase, in retarding the rate of cantaloupe melon peroxidase activity are indicators of the fact that the rate limiting step in the enzymatic reaction proceeds by way of a heterolytic pathway. Mn 2+ was reported to inhibit peroxidase activity in cabbage [26,27], but enhanced peroxidase activity in orange juice [28]. The mechanism for the inactivation of manganese specific peroxidase involves the binding of two Mn 3+ equivalents to the enzyme near the heme, at the expense of one H 2 O 2 [29,30].…”

“…The mechanism for the inactivation of manganese specific peroxidase involves the binding of two Mn 3+ equivalents to the enzyme near the heme, at the expense of one H 2 O 2 [29,30]. The increased inhibitive effects of DETC and tiron that chelate peroxidase molecular iron are also the result of their stronger binding abilities with the enzyme molecule [26,27,31,32]. Tiron, being a radical scavenger retards free radical propagated peroxidase activity [32].…”

Distribution of Polyphenol Oxidase in some Cruciferae Vegetables

“…On the other hand, the purified enzyme of soybean (Toiguchi et al, 1989) and one of the purified enzymes of edible burdock (Murao et al, 1993) not oxidized o-diphenols, but oxidized pyrogallol (1,2,3-trihydroxybenzene) and phloroglucinol (1,3,5-trihydroxybenzene). In addition, a new type of PPO that is "Phloroglucinol Oxidase (PhO)" which only oxidizes 1,3,5-trihydroxybenzene such as phloroglucinol and phloroglucinol carboxylic acid was found in Satsuma mandarin (Fujita and Tono, 1980a) and cruciferae vegetables such as turnip (Fujita and Tono, 1980b) and cabbage (Fujita et al, 1995;1997), and the purified enzymes also had strong POD activities. PPO and POD play roles in darkening of cruciferae vegetables, therefore, the experiments were performed to report the distributions of PPOs of cruciferae vegetables.…”

Oxidases from mate tea leaves (Ilex paraguariensis): extraction optimization and stability at low and high temperatures

“…Peroxidase partially purified from swede and turnip, and commercial high-purity horseradish peroxidase (HRP) decreased their activities after heating at 100°C [15]. Fujita et al [16,17] studied the activities of three isoenzymes from cabbage and pointed out that 50% of PPO activities were retained after heating treatment at 83, 62, and 65°C for 10 min, while 50% of their POD activities remained after the heat treatment at 69, 57 and 53°C for 10 min.…”