Purification and Characterization of Polyphenol Oxidase from Banana (Musa sapientumL.) Pulp

Abstract

Polyphenol oxidase (EC 1.10.3.1, PPO) in the pulp of banana (Musa sapientum L.) was purified to 636-fold with a recovery of 3.0%, using dopamine as substrate. The purified enzyme exhibited a clear single band on polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate (SDS)-PAGE. The molecular weight of the enzyme was estimated to be about 41000 and 42000 by gel filtration and SDS-PAGE, respectively. The enzyme quickly oxidized dopamine, and its K(m) value for dopamine was 2.8 mM. The optimum pH was at 6.5, and the enzyme activity was stable in the range of pH 5-11 at 5 degrees C for 48 h. The enzyme had an optimum temperature of 30 degrees C and was stable even after a heat treatment at 70 degrees C for 30 min. The enzyme activity was completely inhibited by L-ascorbic acid, cysteine, sodium diethyldithiocarbamate, and potassium cyanide. Under a low buffer capacity, the enzyme was also strongly inhibited by citric acid and acetic acid at 10 mM.

Polyphenol oxidase activity and antioxidant properties of Yomra apple (Malus communisL.) from Turkey

“…The general mechanisms of PPO inhibition have been reviewed previously 49,50 . The inhibition values indicate that ascorbic acid and thiol compounds are potent in inhibiting the crude PPO of Yomra apple, and the results are in agreement with previous reports regarding the inhibition of PPO enzyme in many fruits 39,42,51,52 . We conclude that crude extracts prepared from the Yomra apple have a PPO activity very similar to those of other apples and fruits.…”

Inibição do escurecimento enzimático de banana maçã minimamente processada

“…Entretanto, ao contrário do observado no presente trabalho, REIS et al [10] não verificaram influência do tratamento químico contendo AA 1%+CC 1%+Cis 0,5% e AA 1%+CC 1%+Cis 1% sobre as variáveis pH e ATT, durante quatro dias de armazenamento de banana Prata minimamente processada. O escurecimento enzimático é dependente do pH do tecido vegetal, sendo o pH 6,5 ótimo para a ação da polifenoloxidase em bananas [19], acima do observado na polpa da banana maçã.…”

“…Os fenóis encontrados na polpa da banana são oxidados pelas polifenoloxidases, dando origem a quinonas, que se polimerizam e formam os compostos de coloração escura denominados melaninas [15,16]. A polifenoloxidase é capaz de oxidar vários substratos, sendo um deles a dopamina, em um pH ótimo de 6,5, para a polpa da banana [19]. As peroxidases agem desestruturando as membranas celulares, diminuindo sua permeabilidade seletiva; promovem, ainda, reações em cadeia que levam à formação de radicais livres que podem causar danos às organelas e membranas, podendo alterar as características sensoriais do produto [15].…”

Distribution of Polyphenol Oxidase in some Cruciferae Vegetables

“…Table 1 and 2 showed substrate specificity of crude PPO from various Indonesia's and Japan's cruciferae vegetables. Generally, PPO oxidized o-diphenols, as listed in Table 3, garland chrysanthemum (Nkya et al, 2003) strongly oxidized chlorogenic acid and epicatechin; Japanese butterbur ) and apple (Murata et al, 1992) strongly oxidized chlorogenic acid; banana pulp and peel (Yang et al, 2000;2001) (Jia et al, 2011) strongly oxidized catechol. However, substrate specificity of crude PPO from various Indonesia's and Japan's cruciferae vegetables (Table 1 and 2) showed different activity, all the cruciferae vegetables PPOs tested did not show activity toward o-diphenol.…”

“…PPO activity was measured by a colorimetric method (Yang et al, 2000). The mixture to be tested consisted of 0.5 mL of 10 mM aqueous solution of various polyphenols, 4.0 mL of 0.1 M phosphate buffer (pH 7.0) and 0.5 mL of the enzyme solution: it was incubated at 30°C for 5 min and reaction mixture was measured as absorbance at 420 nm (△A420).…”