Strawberry Polyphenoloxidase: Extraction and Partial Characterization

Abstract

Mixing strawberries ground under liquid nitrogen with polyvinylovrrolidone alone or combined with Amberlite XAD4 in oH 4.5 buffer Gelded stable polyphenoloxidase (PPO) extracts. Temperature stability of the enzyme varied with substrate and followed first order kinetics' of inactivation. pH optima were 5.5 with catch01 and 4.5 with 4-methylcatechol. Maximum activity was with D-catechin, followed by 4-methylcatechol and pyrogallol with no cresolase activity. Inhibition occurred with diethyldithiocarbamate, potassium metabisulfite, KCN and dithiothrcitol. Benzenesulfinic acid, cysteine and ascorbic acid blocked the browning reaction without enzyme inhibition. Extraction with Dowex AG 2-X8 resulted in browning. No loss in activity after 95 days occurred with quick-frozen fruit stored under nitrogen at -40°C.

Some kinetic properties of polyphenol oxidase obtained from dill (Anethum graveolens)

“…[22], and Amasya apple [28]. There are a number of compounds such as dopamine [21,60], catechol [21,28,35,45], chlorogenic acid, L-dopa [21,28,35,60], pyrogallol [21,28,35,60], caffeic acid [35,53], p-cresol [21,35,60], tyrosine [21,53], and 4-methylcatechol [21,28,35,45] used as substrates for polyphenol oxidase in the literature. Activation energy (E a ), activation enthalpy(DH a ), and Q 10 determination…”

“…L-cysteine can also act as a reducing agent [35]. Ascorbic acid reduces quinones to hydroquinones and does not directly inhibit PPO [66].…”

“…The pellet was dissolved in 6.0 mL of 0.2 M phosphate buffer pH 6.5 and dialysed at 48C in the same buffer for 24 h with three changes of buffer during dialysis. The dialysed sample was used as the PPO enzyme source in the following experiments [35].…”

Purificação da enzima polifenoloxidase (PFO) de polpa de pinha (Annona squamosa L.) madura

“…Com L-dopa os valores foram de 25,0mM para o K m e de 180,2U/min/mL para V max (Figura 6). A afinidade da PPO pelo substrato, é dependente da origem da enzima (tipo de planta), como foi observado por VAMOS-VIGYÁZÓ [37], WESCHE-EBELING & MONTGOMERY [34,35] e OKTAY et al [31]. …”

Synthesis and theoretical calculations of carbazole substituted chalcone urea derivatives and studies their polyphenol oxidase enzyme activity

“…The extraction procedure was adopted from Wesche-Ebeling & Montgomery 21 . The bananas were washed with distilled water three times to prepare the crude extract, 50 g of bananas were cut quickly into thin slices and homogenized in a Waring blender for 2 min using 100 ml of 0.1 M phosphate buffer, pH:7.3 containing 5% poly(ethylene glycol) and 10 mM ascorbic acid.…”