Characterization of Betacyanin Oxidation Catalyzed by a Peroxidase fromBeta vulgarisL. Roots

Abstract

A protein fraction with peroxidase (EC 1.11.1.7) activity against guaiacol from Beta vulgaris L. roots oxidized both betanidin and betanin (betanidin 5-O-beta-D-glucoside), the former being the more efficient substrate for the enzyme. The protein fraction contained three strongly basic perxidase isoenzymes. Betanidin quinone was formed as the only product in the course of enzymatic betanidin oxidation, whereas betalamic acid and several oxidized cyclo-DOPA 5-O-beta-D-glucoside polymers were generated during the oxidation of betanin. In accordance with the catalytic properties of peroxidase, a possible mechanism for betanidin oxidation is proposed. This mechanism includes the formation of a betanidin radical, which, by further dismutation, yields betanidin quinone and betanidin. The betanidin oxidation rate showed a Michaelis-type dependence on the substrate concentration. The apparent K(M) for the reaction was 0.46 mM. On the basis of the spectral properties of the enzyme responsible for both betanidin and betanin oxidations, its peroxidase nature is suggested.

Inactivation of peroxidase and polyphenol oxidase in red beet (Beta vulgaris L.) extract with high pressure carbon dioxide

“…The main pigment in red beet is a group of bioactive compounds called betalains consisting of betanin, isobetanin, betanidin, isobetanidin, betaxanthins and some other yellow pigments (Schwartz & von Elbe, 1980;Vincent & Scholz, 1978). Like many other natural pigments, betalains are very sensitive to heat, light and oxidation, especially that caused by POD which is one of the major causes of discoloration of the pigment (Lashley & Wiley, 1979;Martinez-Parra & Munoz, 2001;Shih & Wiley, 1981;Wasserman & Guilfoy, 1983). Moreover, enzymatic browning induced by PPO in red beet is another frequently encountered problem in the production of red beet juice (Im, Parkin, & von Elbe, 1990;Lee & Smith, 1979).…”

Betacyanin accumulation and guaiacol peroxidase activity in Beta vulgaris L. leaves following copper stress

“…Sgherri et al [14] have proposed a hypothetical H 2 O 2 scavenging system that comprises phenolics and peroxidase enzymes. The antioxidant activity of betacyanin has been demonstrated in vitro, and betacyanin oxidation by peroxidases of B. vulgaris roots has been described [26,27,46]. The betacyanin-peroxidase system may thus be part of an antioxidant response in B. vulgaris plants to copper stress.…”

Actividad antioxidante y enzimática de albahaca “Nufar” (Ocimum basilicum L.) almacenada en refrigeración.

“…En este contexto, las enzimas polifenoloxidasa y peroxidasa catalizan la oxidación de fenoles a quinonas, las cuales al reaccionar con proteínas y otros compuestos generan colores pardos y reducen las propiedades sensoriales de textura, color y sabor, disminuyendo la calidad nutricional del alimento (Martínez y Muñoz, 2001;Stewart et al, 2001;Ortega et al, 2010). Esto provoca a su vez, un alto porcentaje de pérdida poscosecha en vegetales (Salveit y Morris, 1990;Balois et al, 2008).…”